8: Module 5- Protists - Biology

8: Module 5- Protists - Biology

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8: Module 5- Protists

Year 12 Biology

explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
– animals: advantages of external and internal fertilisation

Lesson 2 | Mechanisms of reproduction in plants

explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
– plants: asexual and sexual reproduction

Lesson 3 | Mechanisms of reproduction in fungi, bacteria and protists

explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:
– fungi: budding, spores
– bacteria: binary fission (ACSBL075)
– protists: binary fission, budding

Lesson 4 | Fertilisation, implantation and hormonal control of pregnancy and birth in mammals

analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals (ACSBL075)

Lesson 5 | Scientific manipulation of plant and animal reproduction

evaluate the impact of scientific knowledge on the manipulation of plant and animal reproduction in agriculture (ACSBL074)

Cell Structure

The cells of protists are among the most elaborate of all cells. Most protists are microscopic and unicellular, but some true multicellular forms exist. A few protists live as colonies that behave in some ways as a group of free-living cells and in other ways as a multicellular organism. Still other protists are composed of enormous, multinucleate, single cells that look like amorphous blobs of slime, or in other cases, like ferns. In fact, many protist cells are multinucleated in some species, the nuclei are different sizes and have distinct roles in protist cell function.

Single protist cells range in size from less than a micrometer to three meters in length to hectares. Protist cells may be enveloped by animal-like cell membranes or plant-like cell walls. Others are encased in glassy silica-based shells or wound with pellicles of interlocking protein strips. The pellicle functions like a flexible coat of armor, preventing the protist from being torn or pierced without compromising its range of motion.

Module 5 / Inquiry Question 1

Before we hop on the materialistic train and start digging into the content, please give me a minute to walk you through what you should keep in mind as the major highlights for this week’s material.

The inquiry (overarching) question for this week deals with reproduction and its relationship with evolution, aka. the continuity of species.

Under the concept of reproduction, we are specifically concerned about the reproductive mechanisms (how they work) occurring in animals, plants, fungi, bacteria and protists.

We need to classify reproductive processes as sexual or asexual on top of how their mechanisms that allow parent(s) producing and passing genetic materials onto their offsprings.

Out of all types of species, NESA wants us to dive into the land of mammals (e.g. reindeer and human) and explore how their reproduction systems work.

We need to understand the process of fertilisation, implantation and hormonal control during reproduction. These stages of reproduction help pass on genetics materials from parent(s) to their offspring.

I am not sure if you are aware but humanity’s scientific knowledge has advanced a lot over the past century.

So, in the last part of this week’s material, we will turn to some real life application examples of humans applying scientific knowledge in genetics and reproduction to create AWESOME variations in plants and animals!

Learning Objective: Explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms.

Did you not knowing or writing out a definition for the main keyword can cost you a mark in HSC Questions?

Let’s first define reproduction!

Reproduction is the process of creating a new individual or offspring from their parent(s).

Reproduction means to reproduce = new offspring. They MAY or MAY NOT be clones of the parent.

Reproduction can be done via natural or artificial means. Hence, the terms natural and artificial reproduction.

There are two reproductive pathways: sexual and asexual. Some organisms can do both!

What are sexual and asexual reproduction and how do they work?

Sexual reproduction: The process of forming a new organism from the fusion of the offspring’s parents’ (male + female) gametes. Gametes are sex cells such as sperm and egg cells for humans. The offspring that is formed from sexual reproduction has the genetic material that is derived from its parents. However, in almost* all cases the offspring’s genetic material is NOT IDENTICAL to their parents (it’s mixed). In humans and many other mammals such as cows this process of producing gametes is called meiosis .

*Note that self pollination involves one plant (parent) and is a type of sexual reproduction. This is because the plant can produce both pollen and ovules (male and female plant gametes). These gametes can combine to produce either a genetically identical offspring or genetically different offspring. Whether the offspring is genetically identical or different, it will depend of whether the single parent plant is homozygous or heterozygous for those genes. We will learn about these two terms when you learn about Punnett Square in Week 4’s notes.

Asexual reproduction: Asexual reproduction is the process of forming an offspring (usually a cell) from just ONE parent through cell division. Depending on the cell division process, there may be many names. For example, in humans and many other mammals, this cell division process is called mitosis . Thus, the offspring has genetic materials that is IDENTICAL to that of its single parent – offspring is a CLONE of the parent.

The most important distinguishing factor between sexual and asexual reproduction is whether or not the fusion of gametes occurred. For sexual reproduction, there must be a fusion of gametes whereas, in asexual reproduction, there is no fusion of gametes.

How sexual and asexual reproduction processes allow parents’ genetic information to be passed on to their offspring, and thus, ensuring the continuity of the species?

During reproduction, the parents’ genetic information (DNA) is copied and passed onto the offspring. The offspring’s genetic material is stored in their cells’ nucleus.

There are two types of cells: somatic and non-somatic (sex) cells. Since humans and many other mammals cannot produce offspring via asexual means, all offsprings produced are from non-somatic cells. Hence, only the parents’ genetic material in non-somatic cells’ (or sex cells’) genetic material is passed onto the offspring.

Genetic information is passed onto the next generation (offspring). Thus, ensuring the continuity of the species.

By week 3’s notes, you will see the importance of creating variation in offspring’s genetic information (new allele combinations, increasing variation in the alleles which gametes can inherit as well as variation in the gametes that are fertilised during fertilisation). Don’t worry if you don’t know what genes and alleles are, we will look into their definitions and role in genetics in Week 2. Essentially, the point is that you will see how the increased variation in the offspring’s genotype will enhance the chances of survival of a species’ population and thus supporting the continuity of the species. In Week 4’s notes, you will see how mutation (apart from sexual and asexual reproduction) can also create genetic variation.

A third point is that reproduction would increase the total number of offsprings in a population, effectively increasing population size. Thus, supporting the continuity of species.

What is evolution?

Evolution is the change in living organism’s genetic information, favourable characteristics and phenotypes (appearance or physical traits) over many generations.

For now, just know that genetic information contributes to an organism’s phenotype. In terms of how this works, this will be comprehensively covered in the upcoming weeks.

But what drives evolution aka. the change in genetic information, for example, how a rainbow unicorn population can slowly turn into a pack of green unicorns, over time?

How and where does reproduction fit in Darwin’s Theory of Evolution by Natural Selection?

Darwin’s Theory of Evolution by Natural Selection is a popular and widely accepted modern theory of evolution.

It explains the drivers and consequences of evolution to a reasonable extent.

It, however, fails to account the origins of life on Earth or any place in our universe from start to finish.

There are other models that deals with the origin of life and such as the RNA world hypothesis but they are not complete.

Please keep in mind that these are all theories! Yes, there are evidence to back them up. However, existing evidence is not complete to transform these theories into universal laws!

In order, here are the Stages of Darwin’s Theory of Evolution by Natural Selection:

1. There is genetic variation in population, which affects it phenotype (physical traits). The genetic variation is derived from a number of factors – from internal biological processes to external environmental factors. These factors will be comprehensively covered in later weeks.

2. The majority of the existing population would have the favourable traits that allow them to survive in the environmental conditions (temperature, food supply, predators, etc) that they are exposed to.

3. There is a SUDDEN change in environmental conditions (e.g. new predator introduced to kill the unicorns, sudden large drop in temperature, a virus, etc)

4. Those organisms with favourable characteristics, derived from favourable genes passed on from parents, will survive and those with less or without favourable characteristics will decline in numbers.

5. Those organisms with favourable characteristics will reproduce more successfully and pass on their favourable genetic information to their offspring. REPRODUCTION FITS IN HERE!

6. Over time, the new population will predominately be made up of organisms with favourable characteristics that allow them to tolerate the new environmental conditions.

The environmental agent is refers to the environmental change. This could be a exotic species introduced into the habitat (e.g. from migration) that is competing for the same food resource as the existing population, a new predator, introduction of chemicals into the environment – e.g. toxic wastes being throw into the river, home to thousands of fish..

It is called Darwin’s Theory of Evolution by Natural Selection because there is a sudden change is due to environmental (nature) change(s).

What are favourable characteristics in Darwin’s Theory of Evolution?

How can organisms acquire these awesome characteristics?

Favourable characteristics that allow organisms to survive in their environment can take three forms:

Physical, Physiological and Behavioural.

‘Favourable’ means that these characteristics allow the organism to specifically or better cope with its ambient environment.

As these characteristics are derived from genetic material INHERITED over generations, they are also referred to as adaptations.

For HSC purposes, an organism CANNOT adapt to its environment during its lifetime.

Adaptations are inherited.

Example: A snake cannot learn to seek shade to prevent itself from overheating during its lifetime if it did not inherit such behavioural characteristics from its parents.

However, you will learn later in Module 6 that a mutation can also give rise to adaptation.

The following characteristics or adaptations are evolved through many generations:

Physical characteristics (PHENOTYPE): Large ears to facilitate cooling. This is favourable for organisms living in hot environments.

Physiological characteristics: Kangaroos licking their paws to encourage evaporation and cooling down. Favourable in hot environments.

Behavioural characteristics: Snakes hiding under rocks to avoid the sun. Favourable in hot environments or during the middle of the day.

In Step 1 of Darwin’s Theory of Evolution by Natural Selection, it was mentioned that there is genetic variation in the population. The main sources of variation are:

Mutation of DNA as a result of environmental factors

DNA replication error during meiosis

Independent assortment and random segregation during meiosis

We will go into details of these sources of variation in the later weeks.

For now, just understand where these factors fit in within the areas of evolution and reproduction that we covered so far.

NOTE: It is important to note that asexual reproduction does not introduce genetic variation in offspring while sexual reproduction does. Despite this, the parent of the offspring has favourable characteristics (adaptations) to allow the parent to tolerate the selective pressures of the ambient environment, asexual reproduction allows the parent to produce offspring with IDENTICAL genetic information (no genetic variation) that codes for the same favourable characteristics (e.g. long or short ears depending on environment temperature). The offspring will now have the same favourable characteristics as parent due to inheriting identical genetic information and thus have the same survival rate of parent if they are exposed to same environment with the same resources.

RECAP on what we covered so far,

Two categories of reproduction that can take place (sexual & asexual)

Reproduction allows genetic information to be passed on to offspring via heredity, ensuring continuity of species

Reproduction increases population size thus supporting the continuity of species

Genetic variation helps increase the population’s overall survival rate and thus support the continuity of species.

Sexual and asexual reproduction are both useful in supporting the continuity of species despite asexual reproduction not introducing genetic variation in offspring and, thus, population.

Reproduction plays an important role during Darwin’s Theory of Evolution via Natural Selection

We will now explore the SPECIFIC TYPES OF REPRODUCTION in the sexual and asexual reproduction categories!

This is very eggciting! Get the joke? Sorry, I needed to do it.

Analyse whether the types of reproduction methods are sexual or asexual?

How do they work?

Internal fertilisation vs External Fertilisation

Internal fertilisation involves the fusion of male and female gametes within a parent’s body. Internal fertilisation tends to occur between terrestrial animals.

External fertilisation involves the fusion of male and female gametes outside a parent’s body. External fertilisation tends to occur between aquatic animals.

Parthenogenesis in animals

Parthenogenesis is the process whereby an unfertilised egg develops into an functional offspring. This is a form of asexual reproduction in animals, e.g. bees. For bees, queen bees can produce egg cells (gametes) via meiosis. These egg cells can undergo parthenogenesis to produce haploid drone (male) bees. Haploid cells are cells that have half the amount of chromosome as parent. Chromosomes contain DNA which you will explore in Week 2 notes. Usually parthenogenesis occurs due to the organism’s hardship in having access to mating partners. This is common for organisms residing in harsh or extreme environments. For the most part, the haploid cell develops as it would it would a diploid cell. So, essentially, the gamete undergoes mitosis to develop into a drone bee which will have a diploid chromosome number.

Plants can also undergo parthenogenesis which is called apomixis.

Mechanisms of Cross-Pollination vs Self-Pollination

Cross pollination involves the transfer of pollen, produced by anther (which is part of the plant’s stamen), to the stigma of another plant. This means that cross pollination involves two plants. The pollen grain essentially contain the male gametes of the plant. Bees, wind and water can be transport methods of pollens grain to stigma of another plant for cross pollination. Pollination is referred to the process where the pollen is successfully transfered to the stigma of another plant.

Once the pollen is on the stigma, it can grow a pollen tube which runs down the style of the plant and eventually into the ovary of the plant which produces the ovules which contains female gametes (ovum or ova) of the plant. Fertilisation occurs inside the ovule where the pollen can fertilise the ovule where male gametes are combined with the ovum inside the ovule forming a zygote. The zygote is diploid, i.e. has double the chromosomes of each of the male and female gametes which are both haploid. We will discuss more of diploid and haploid when we explore Mitosis and Meiosis next week.

Note that most pollen grains contain two male gametes. One fertilises the ovum inside the ovule and the other male gamete fertilises two polar nuclei (diploid nucleus) inside the ovule which develops into a endosperm which is a tissue that supply nutrients to the zygote (seed) when it grows.

Fun fact: This means that the endosperm nucleus is a triploid (contains three sets of homologous chromosomes or three copies of each chromosome). Humans are diploids (we contain two sets of chromosomes, i.e. two copies of each chromosome).

Note that chromosomes in the homologous sets are not necessarily identical copies as the chromosomes may contain different alleles for the same gene. We will explore more about alleles next week.

This fertilised ovule is called a seed which contains the zygote and will develop into an embryo. In some plants, the surrounding space of the ovule will develop into a fruit. Other plants such as sunflowers do not form fruit, what happens is that the seed will drop from the original sunflower which will develop into another sunflower when the seed germinates under the favourable conditions. The seed will germinate (grow) into a plant via mitosis. In some other flora, the ovary will become a fruit. However, this is not for sunflowers as they do not grow fruits XD.

It is important to note that most plants have its own stigma and stamen. Self-pollination is similar to cross pollination. The difference between self-pollination and cross-pollination is that self-pollination does NOT involve a an external agent such as bees, water and wind as mentioned previously. Instead, the stigma can reshape itself to enclose the stamen. This means that the pollen can be easily transferred onto the stigma.

It is important to note that self pollination causes the resulting flower offspring (after seed germination) to have far less genetic variation than their parents in most cases compared to cross pollination. This is because the resulting flower is only produced from only one parent plant rather than two in cross pollination. If the parent in self-pollination is heterozygous for some genes, the resulting flower may have probabilities of being genetically different to their parents for those genes. We will examine why this is the case when we do Punnett Squares in Week 4 where we learn about homozygous and heterozygous alleles for different genes.

Cross pollination will result in a sunflower offspring that genetically different to its parents. It involves the transfer of pollen from one plant to the stigma of a different plant.

Vegetative Propagation

You may have heard of vegetative propagation at school. How does vegetative propagation fit in all of this?

Well, vegetative propagation is a type of asexual reproduction that occurs in plants. It results in the parent producing a plant that is genetically identical. Runners, bulbs, fragmentation are some examples of vegetative propagation. Let’s have a look at them now.


Fragmentation is when the original organism separates a small part of itself. This occurs in starfish where a part of its body can be separated from its parent and the separated section can develop into a new starfish that is genetically identical to parent starfish via cell division.

Fragmentation can also occur in mosses when you split one moss into two. The moss will grow via cell division when it becomes into contact with matter such as moisture in the air.


Strawberry plants can develop runners which are stems extending from the plant and along the soil. At certain points along the runners, nodes can develop which extends to the soil, resulting in the formation of new plant roots at another area of the soil whereby a new strawberry plant can grow. The runner joins the new (and genetically identical) strawberry plant to the parent plant.


Bulbs are bud cells that are found underground. These buds can develop into new plants such as onions. When a new plant forms, the underground bulb provide nutrients to the plant for its survival.

Budding in Fungi

Budding in fungi such as yeast involves the parent cell developing a bud cell, a daughter nucleus. This usually occur when the environmental conditions are favourable for the fungi. Over time, this bud undergoes cell division while still being attached to the parent which may result in a chain of bud cells due to cell division. During cell division, but prior to separation of the protruding bud from the parent yeast (fungi), the parent’s nucleus’ DNA replicates and nucleus divides equally, but, the cytoplasm divides unequally (hence bud is smaller than parent). One copy of the DNA moves into the bud cell which results in the successful transfer of the parent’s DNA into the daughter (bud) cell. The bud separates from its parent fungus when it grows to a sufficient size to be able support itself independently. This now-separated bud undergoes further cell division to produce more bud cells. The result is yeast that is genetically identical to parent.

Budding is also found in another type of organism called Hydras and the budding process is similar to that of fungi.

Asexual spore production in Fungi

Spores are microscopic reproductive units (cells) that can be formed as a result of mitosis or meiosis.

Spores different to gametes as they do NOT need to combine or be fertilised by another spore to form an offspring.

Mycelium is part of a fungi that branches out into a network structure of fine ‘threads’ called hyphae (plural for hypha). Each hypha have ends of that are capable of producing spores called sporangia (plural for sporangium). These sporangia (and thus spores) are produced when environment conditions are favourable for the fungi’s survival. Mushroom is a type of fungi where the mushroom cap is above the hyphae spread along the stem and to the mushroom cap. The mushroom cap therefore has basida, which are examples of sporangia, that produces spores.

These asexual spores are usually produced when ambient environment conditions are favourable via mitosis. These spores are usually carried by the wind as they are light-weight. These spores then germinates to form genetically identical fungus when environmental conditions are favourable. This typically involves the spores absorbing moisture and decaying organic matter from its environment, allowing the cytoplasm to expand and the fungus developing into a mycelium whereas new spores can be produced.

Sexual spore production in Fungi

Sexual spores are developed when opposite gender hyphae are combined together to develop a sporing-producing structure known as zygospore. The zygospore is diploid as each of the hypha are haploid. Under favourable conditions, the diploid zygospore undergoes meiosis to produce haploid sexual spores which are dispersed into the environment. These spores that are genetically different from their parents.

Under favourable conditions, these spores will germinate and a genetically different fungus to its parents will be formed. These fungi are haploid as most fungi spend their lives as haploid organisms until time of sexual reproduction where hyphae combine to form a diploid zygospore to produce haploid sexual spores.

In some fungus, the mycelium contains hyphae of two genders (male and female). This means that these fungus can produce spores via meiosis and disperse them into the environment.

The term ‘plasmogamy’ refers event where the nucleus of the one hyphae enters the cytoplasm of another hyphae.

The term ‘karyogamy’ refers to the event where the two nucleus are combined into one.

Binary fission in Bacteria

Binary fission is most commonly performed by unicellular organisms such as bacteria, though some multiceullar organisms can reproduce asexually via binary fission too. The process starts with the copying the genetic material (in the form of bacterial chromosomes) of the parent cell. Each chromosome moves to each side of the cell. This is followed by the elongation of the cell and cytokinesis which is the splitting of the cell membrane and cytoplasm of the cell into two daughter cells. As there is no cell nucleus in bacteria, there will not be the splitting of cell nucleus. It is important to note that the parent cell won’t exist at the end because it is now part of the two daughter cells. The two daughter cells are genetically identical to each other as well as identical to the parent which they obtained their genetic information came from.

NOTE: There are multicellular organism that reproduce asexually via binary fission. However, they are uncommon. Some example of this is the organism named Trichoplax.

Budding in Protists

Budding in protists is a type of asexual reproduction. In short, budding in protists starts off by the parent protozoan producing a bud which is a daughter nucleus that is created based on the replicate of nucleus DNA, followed by equal nucleus division but unequal separation of the parent protozoan’s cytoplasm. This means that the bud is smaller than the parent. Over time, this daughter nucleus undergoes further cell division via mitosis to grow and mature, resulting in a protists that is genetically ideal to parent.

Binary fission in Protists

The mechanism of binary fission in protist is similar to that of bacteria’s binary fission process. However, as DNA is stored in the nucleus (whereas no nucleus in bacteria), the chromosome will move to each side of the nucleus before the splitting of the nucleus and eventually splitting of the cell membrane and cytoplasm into two daughter cells. The splitting of the parent cell into two daughter cells is called cytokinesis.

NOTE: Binary fission in protist vs bacteria and budding in protist vs fungi are similar. So, it is important to determine the unique characteristics fungi and protist.

Protists are mostly unicellular whereas fungi are mostly multicellular.

Protists are microscopic whereas fungi are macroscopic.

Protists are eukaryotes whereas bacteria are prokaryotes.

Advantages and disadvantages of internal and external fertilisation

Internal fertilisation

• Internal fertilisation occurs inside the female’s body which means that the zygote is protected from the external environment of the parent. This means there are less environmental factors that affect the zygote in internal fertilisation compared to external fertilisation. This increases the survival of the zygote.

• Internal fertilisation is NOT restricted to terrestrial environments unlike external fertilisation which is restricted to aquatic environments only.

• Internal fertilisation has higher fertilisation success rate on a per gamete basis compared to external fertilisation. This is because the sperm does not need to travel by chance to fertilise an egg. Internal fertilisation provides the sperm a direct route towards to egg cell inside the female’s body. During such journey, the sperm cell is subjected to less variable and/or violet environment factors such as strong current or predators.


• Internal fertilisation typically have less mating partner options than external fertilisation. This can lead to a lower genetic variation in species population as the mating process is more selective than external fertilisation

• Internal fertilisation generally required more energy in search for a mating partner and perform the mating process which are unnecessary in external fertilisation.

• Less gametes are produced via internal fertilisation compared to external fertilisation. This leads to a lower overall amount of offsprings produced. Arguably, this means that internal fertilisation may low the chance of the continuity of a species (if we assume that genetic variation is controlled for both internal and external fertilisation, i.e. genetic variation is the same for both external and internal fertilisation).

External Fertilisation

• Greater quantity of gametes are produced via external fertilisation compared to internal fertilisation. This leads to a greater overall amount of offsprings produced. Arguably, this could supports the continuity of species more than internal fertilisation.

• External fertilisation can give raise to more mating partner options than internal fertilisation. This can lead to greater genetic variation in species population as the mating process is less selective than internal fertilisation.


• Upon fertilisation, the zygote is exposed to the environment rather than protected inside the mother’s body for internal fertilisation. Due to the limited defence capabilities of the zygote (e.g. against predators), it is more susceptible to death than zygotes found via internal fertilisation. Most of the gametes are being attacked by predators or fail to be fertilised. The zygote therefore has a lower chance of survival via external fertilisation.

External fertilisation is restricted to aquatic environments. The flagellum component of the sperm cell allows it to move through water that otherwise would not be possible on land. If performed on land, the egg will dry out.

External fertilisation has a lower fertilisation success rate than internal fertilisation. This is because the sperm and egg cells are subjected to greater amount of factors in external fertilisation than internal fertilisation. For example, the more environmental factors such as predators (Sea life) and harsh aquatic environment conditions (e.g. harsh currents).

Example of a case of external fertilisation (Sea urchin):

Male and female sea urchins produce gametes which are dispersed in the ocean.

Male salmon produce gametes (Sperm) to fertilise a nest of eggs that is produced by female salmon somewhere in the ocean.

Extra Notes on sexual and asexual reproduction

Now that we have explored asexual and sexual reproduction with examples, let’s see what they involve beyond differences between number of parents involved and genetic variation in offspring that we have mentioned at the beginning of this notes.

Here are some extra notes between sexual and asexual reproduction:

Sexual reproduction requires more energy than asexual reproduction.

However, asexual reproduction tends to occur at a faster rate than sexual reproduction.

Genetic variation is created in sexual reproduction and NOT in asexual reproduction.

Genetic variation increases the likelihood of the continuity and evolution of the species – relating back to inquiry question.

Asexual reproduction would also be a concern if the parent genes code an unfavourable trait because there is no other source of genes from another parent to override it.

This problem is reduced in sexual reproduction as the offspring’s genome is a mix of both parents (rather than single parent) and unfavourable trait could be overridden.

More details about overriding genes in later weeks. It is based on concepts of dominant and recessive genes.

Asexual reproduction generally ONLY take place because the ambient environment conditions are favourable as asexual reproduction does not increase variability in genetic materials.

An asexual offspring is a clone of its parent. If one clone is affected, the whole cloned population have equally as great of a danger for extinction.

Well done! we have broadly covered reproduction processes for a range of organisms. We will now examine reproduction for mammals specifically!

Learning Objective: Analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals


Requires gametes (sperm and egg) meet and combine to form a zygote

Gametogenesis is the name of the gamete formation process.

Gametogenesis can be divided into spermatogenesis (producing sperm) and oogenesis (formation of matured egg cells)

The hormone testosterone is produced in cells’ in the testes organ of male as part of spermatogenesis as it plays a role in producing sperm cells.

The hormone oestrogen in males help with the maturing of the sperm cells in males.

The fertilisation process and fusion of gametes occurs in the fallopian tube of female’s body

The zygote will develop into a living organism that has mixed genetic information from the parents.

Zygote is the continuity of a species (relating back to inquiry question)

Fertilisation involved multiple stages that MUST be fulfilled for successful fertilisation and zygote formation and thus producing a new offspring.

Three necessary stages for successful fertilisation are:

Formation and maturation of gametes

Spermatozoa must journey into the oviduct

Spermatozoa must make contact and fuse with the egg cells.

The gametes fuse with one purpose – to form a zygote, single cell with 46 chromosomes

During fusion, the head of the sperm cell detaches from its tail (flagellum) and the sperm-egg species journeys down the female’s uterus.

Also, during fusion, the sperm cell activates the egg cell resulting in cell division of the egg cell growth/development. The resulting product is called a blastocyst.

Once the sperm fused with the egg, other sperms will no longer be able to fuse with the same egg

Most of our contemporary knowledge of fertilisation in mammals comes from laboratory testing with mice gametes.

The gametes must be from the same species in other for successful fertilisation.


Implantation is the process of adhering the fertilised egg to stick to the walls of the reproductive tract, providing the most suitable environment for zygote development.

It is a crucial phase for successful pregnancy.

The blastocyst is implanted on the walls of the reproductive tract (uterine wall).

Successfully implantation means pregnancy.

This implantation process onto the walls establishes blastocyst’s access to nutrients to develop into an embryo (blood vessels surrounding the blastocyst carries blood which has dissolved nutrients)

Embyro develops into a fetus (approx 5-11 weeks)

Embryro becomes a new organism upon release from female’s body.

The bottom left image is diagram showcasing the steps of fertilisation and implantation:

The idea of the diagram is just to allow you have a rough idea of where fertilisation and implantation occurs in the female’s body. The steps in the diagram not as important.

Note, at ovulation stage, the matured egg cell is released from the follicle and travels up and along the fallopian tube (the C-shaped tube as shown in diagram below) that connects the ovary to the uterus. It at the uterus where the embryo is implanted on the uterus wall (endometrium) during implantation phase.

Successful implantation of the embryo means successful pregnancy.

Note that: When the sperm enters the vagina, up to the uterus, along and down the fallopian tube where it can combine and fertilise the mature egg. This means that the mature egg and sperm encounter each other head-on as the egg is moving in the direction from ovary to uterus and sperm is moving in the direction of uterus to ovary.

This means that they are likely to meet at the fallopian tube, which is where fertilisation of the mature egg cell most commonly takes place in reality.

In the diagram below, we see that the zygote (fertilised egg) is formed in the fallopian tube where the sperm meets and fertilises the egg.

Facts about Protists

The earth consists of millions of organisms both big and small. Each of these organisms further have their own history of existence.

If viruses are not included as live, protists fall under the category of the smallest group of living things.

According to Scientists, protists are believed to have paved the way for evolution of early plants, animals, and fungi. Protists fall into four general subgroups: unicellular algae, protozoa, slime molds, and water molds.

The name Protista means “the very first” and there are 80-odd groups of organisms that are classified as protists. They have been in the evolutionary history as early as 2 billion years. However, Genome analysis of their genomes by biologists shows that they are not really as primitive as they were originally believed.

1. All unicellular organisms, which are not prokaryotes, are classified under Protists.

They have a well-defined nuclear membrane and also contain mitochondria and some have chloroplast.

2. They are found in many different forms.

They are either synsytial or multicellular. They can be found as colonies or as filaments or a leaf like, multicellular structure or body composed primarily of a single undifferentiated tissue.

3. All protists are not microscopic.

Among the brown algal protists, some forms may reach a length of 60 metres or more, although the normal range is 5 micrometres to 2 or 3 millimetres. Some parasitic forms and a few free-living algal protists may have a length of 1 micrometre as well.

4. They can be motile or non-motile.

Many protists are capable of motility by means of flagella, cilia, or pseudopodia. There are other groups of protists which may be non-motile during part or most of the life cycle.

5. Nutrition is by different modes.

Their modes of nutrition include photosynthesis, absorption, and ingestion. Some species exhibit both autotrophic and heterotrophic nutrition.

6. Flagella and cilia are also involved in sensory function

The outer membrane contains several receptors at the molecular level. There are seven kinds of receptors. A variety of chemoreceptors can recognize minute changes in the medium surrounding the organism.

7.Protists also have pseudopodia.

Pseudopodia are responsible for amoeboid movement. This type of locomotion is associated with members of the protist group called the Sarcodina. Pseudopodia are used in both phagotrophic feeding, as well as in locomotion. There are different kinds of pseudopodia. Three kinds of pseudopods (lobopodia, filopodia, and reticulopodia) are similar, and are frequently found among the rhizopodsarcodines, while the fourth type (axopodia) is different. They are more complex, and characteristic of actinopodsarcodines.

8. Respiration is a very simple process.

It is by the direct diffusion of oxygen from the surrounding medium. There are two groups that also exhibit anaerobic metabolism: parasitic forms and some bottom-dwelling ciliates which live in the sulfide zone of certain marine and freshwater sediments.

9. Feeding is through diverse mechanisms.

It is by capture of living prey by the use of encircling pseudopodial extensions. Trapping of food particles in water currents, is by filters formed of specialized buccal organelles and by simple diffusion of dissolved organic material through the cell membrane. In the case of Parasiticprotists, it is by sucking out of the cytoplasm of host cells.

10.There are different methods by which protists reproduce.

Reproduction is by binary fission, multiple fission or by conjugation.

11. Some major diseases of humans are caused by protists

Malaria is caused by a protozoan protist of the phylum Sporozoa .Various trypanosomiases (e.g. sleeping sickness) and leishmaniasis are due to different protists

12.Protists are used as cell models in biological research

Unicellular free-living protists can be cultured easily and hence are invaluable as assay organisms and pharmacological tools. The best example is the ciliate Tetrahymena, which serves as a model in cell and molecular biology.

5.8 Diseases caused by fungi and protists NEW GCSE Biology specification

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Content is for the NEW AQA GCSE biology specification.
This lesson plan/PowerPoint presentation contains all the activities and resources (within one file!) to achieve the following learning objectives:

1) Give examples of plant diseases caused by fungi, including rose black spot - Guess if the disease is caused by a fungi or protist starter activity

2) State examples of animal diseases caused by protists, including malaria - Malaria information sheets (in PowerPoint ready for printing!), corresponding questions including differentiation answers included in the PowerPoint for peer or self-assessment.

3) Explain how the spread of diseases can be reduced or prevented - Malaria task as above AfL in plenary activities.

Choice of two plenary tasks recapping fungi and protist diseases (answers included) or gap fill exercise depending on time available (answers included).

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Communicable diseases: Viral diseases, Diseases caused by fungi & protists, More about plant diseases and Plant responses

Includes PowerPoint presentations with interactive pupil led activities for the following lesson sequence: 5.6 Viral diseases 5.8 Diseases caused by fungi and protists 5.10 More about plant diseases 5.11 Plant responses

Communicable diseases: Diseases caused by fungi & protists, Plant diseases & Responses, Viral diseases, Bacterial diseases & Preventing Infections plus Crossword set

Bundle of six GCSE Biology lessons with fun, engaging and interactive activities including: 5.5 Preventing infections 5.6 Viral diseases 5.7 Bacterial diseases 5.8 Diseases caused by fungi and protists 5.10 More about plant disease (Biology only - aka Triple Science) 5.11 Plant disease responses (Biology only - aka Triple Science) Complete set of crosswords for the whole chapter on communicable disease.

Protists Examples

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The descriptions of protists are presented in the following paragraphs. Important examples of such organisms include the amoeba, diatoms, euglena, and paramecium.

Amoeba: Discovered by August Johann Rösel von Rosenhof in the year 1757, amoeba was referred to as Proteus animalcule by the naturalists of earlier times. The Amoeba proteus is a commonly found species of this microbe. Its size ranges from 220 – 740 micrometers. Their body structure is characterized by the presence of a single or more than one nuclei. Reproduction takes place asexually, in the form of cytokinesis.

Euglena: It is a unicellular microbe, which has more than 1000 species. These organisms exhibit both autotrophy and heterotrophy. The former ones produce sugars by the means of photosynthesis. Raw materials used in this process include the carotenoid pigments, chlorophyll ‘a’ and chlorphll ‘b’. Owing to the dual characteristics of plants and animals possessed by the euglena, there is confusion over how to classify them. Reproduction takes place asexually in the form of binary fission. Flagella are the organs used for locomotion. Eyespot is the part of euglena’s body that is photo-sensitive. Light is detected with the help of this part, and necessary adjustments for photosynthesis are made.

Diatom: It is a phytoplankton that forms one of the important groups of algae. Most of the diatoms are unicellular in nature. Their cell wall is known as frustule, which is made up of hydrated silicon dioxide. There is a great variety in the forms of these frustules. Diatoms are found in freshwater bodies like rivers and lakes, and also in oceans. The 100,000 species of diatoms are grouped under 200 genera. They prove to be useful from the point of studying water quality of a particular area. Most number their species are found in the tropical regions. Binary fission is the mode of reproduction used by diatoms.

Paramecium: These are unicellular microorganisms, which possess the locomotory organ called cilia. Their body length ranges from 50 – 350 micrometers. Contractile vacuoles are used by the paramecium for the purpose of osmoregulation. The oral groove is a part of this organism present on the side of its body. Intake of food (with a sweeping motion) is the function of the oral groove. Yeasts, algae, and bacteria form the diet of this organism. These microbes are commonly found in freshwater regions. Few of the paramecium species can also be found in oceans. Bacterial endosymbionts and Paramecium aurelia share symbiotic relationship with each other.

Microbes are amongst important living beings found on earth. The examples of protists and their characteristics presented in the above paragraphs should help you to understand more about these organisms.

Types and examples of Protists

Biologists consider protists as a polyphyletic group, which means they probably do not share a common ancestor. The word protists comes from the Greek word for first, indicating that researchers believe protists may have been the first eukaryotes to evolve on Earth. Now, the Protists are classified in to three main types or subdivisions on the basis of their similarity with other kingdoms. These are

  • Protozoa (animal like protists)
  • Molds (Fungus Like Protists)
  • Algae ( Plants like Protists)

A) Protozoa (animal like protists)

Protozoa are single-celled organisms. These are also called animal like protists. All protozoa are heterotrophic, that is, they feed on other organisms to obtain nutrition. There are also parasitic protozoa that live in the cells of larger organisms.

Protozoa can be divided into four main groups:

  1. Phylum Sporozoa (Parasitic Protozoans): e.g. malaria
  2. Phylum Ciliophora (Ciliated Protozoans): e.g. paramecia
  3. Phylum Rhizopoda (Amoeboid Protozoans): e.g. amoeba
  4. Phylum Zoomastigophora (Flagellate Protozoans): e.g. Trypanosoma

1- Phylum Rhizopoda (Amoeboid Protozoans): e.g. amoeba

  • These are a group of protozoa characterized by their amoeboid movement through temporal projections called pseudopodia.
  • They are found mainly in bodies of water, either fresh or saline.
  • They have pseudopodia (false feet) that help change their shape and capture and wrap food. e.g. Ameba “Amoeboid cells may also produce in fungi, algae, and animals”

2- Phylum Zoomastigophora (Flagellate Protozoans): e.g. Trypanosoma

  • As the name suggests, These protozoans have one or more flagella for locomotion and sensation. A flagellum is a structure resembling hair capable of lashing movements similar to lashes that provide locomotion.
  • They can be free-living (Euglena) as well as parasites (Trypanosoma).
  • Parasitic forms live in the intestine or bloodstream of the host.
  • They may also be colonial (volvox), Solitary (Phaeocystis)

3- Phylum Ciliophora (Ciliated Protozoans): e.g. paramecia

  • The ciliates are a group of protozoa characterized by the presence of hair-like organelles called cilia, whose structure is identical to that of eukaryotic flagella, but which are generally shorter and present in much greater numbers, with a wavy pattern.
  • The cilia help in locomotion and obtaining nutrition.
  • These are single-celled organisms and are always aquatic.
  • Paramecium is a model ciliate living in freely in freshwater. The most widely distributed species are Paramecium caudatum and Paramecium aurelia.

4- Phylum Sporozoa (Parasitic Protozoans) e.g. the malaria parasite, Plasmodium

  • These organisms are named so because of the presence of spores in their life cycle.
  • Sporozoa have neither flagella, eyelashes, nor pseudopodia. They are able to slip movements.
  • All Sporozoa are parasites of animals and cause disease.

B) Molds (Fungus Like Protists)

Molds are saprophytic organisms (they feed on the dead and decomposing matter). These are small organisms that have many nuclei. Molds are usually characterized by the presence of spores and are even visible to the naked eye. Basically they are divided into two types, viz. Water molds and Slime molds.

Oomycota or oomycetes (generally called water molds)

  • These are a group of filamentous protists that physically resemble fungi and are heterotrophic.
  • They are microscopic, absorptive organisms that reproduce both sexually and asexually and are made of a tube-like vegetative body called mycelia.
  • These may be free-living or parasitic. The parasitic form may grow on the scales or eggs of fish, or on amphibians or plant bodies.
  • A notorious example of water molds is Phytophthora infestans, a microorganism that causes the serious potato and tomato disease known as late blight or potato blight.

Myxomycota or myxomycetes ( generally called as Slime mold)

  • Slime molds are several kinds of unrelated eukaryotic organisms that can live freely as single cells but can aggregate together to form multicellular reproductive structures.
  • These grow as a naked network of protoplasm that engulf bacteria and other small food particles by phagocytosis.
  • Slime molds are common in moist, organic-rich environments such as damp, rotten wood, where there is an abundance of bacteria as a food source. They are mostly seen as they begin to sporulate because of their conspicuous and brightly colored fruiting bodies.
  • They may be
  1. Plasmodial slime molds such as Physarum species
  2. Cellular slime molds which are unicellular amoeboid organisms such as Dictyostelium
  3. Endoparasitic slime molds such as the Plasmodiophora brassicae that causes clubroot disease of cruciferous crops.

C) Algae ( Plants like Protists)

These form another category under the Protista kingdom. These are generally unicellular or multicellular organisms. These are photosynthetic, they are found mainly in freshwater sources or marine lakes. They are characterized by a rigid cell wall.

Types of Algae

There are seven main types of algae that are following.

  • Green algae (Chlorophyta)
  • Euglenophyta (Euglenoids)
  • Golden-brown algae and Diatoms (Chrysophyta)
  • Fire algae (Pyrrophyta)
  • Red algae (Rhodophyta)
  • Yellow-green algae (Xanthophyta)
  • Brown algae (Phaeophyta)

Green algae (Chlorophyta)

Examples: Chlorella, Chlamydomonas, Spirogyra, Ulva. Green algae.

  • The green color pigments i.e. chlorophyll a and b are present in the Chlorophyta.
  • Food reserves of Chlorophyta are starch, some fats or oils like higher plants.
  • Green algae are believed to have the parents of higher green plants.
  • Green algae can be unicellular (having one cell), multicellular (having many cells), colonial (many single cells living as an aggregation), or coenocytic (composed of a large cell with no crossed walls the cell can be uninucleated or multinucleated).

Euglenophyta (Euglenoids)

Examples: Euglena mutabilis or Colacium Sp.

  • Euglenoids are single-celled protists that occur in freshwater habitats and wet soils.
  • These actively swim in an aquatic environment with the help of their long flagellum. They can also perform creeping movements by expanding and contracting their body. This phenomenon is called the euglenoid movement.
  • They have two flagella at the anterior end of the body.
  • There is a small light-sensitive eyespot in their cell.
  • They contain photosynthetic pigments like chlorophyll and therefore can prepare their own food. However, in the absence of light, they behave similarly to heterotrophs when capturing other small aquatic organisms.
  • They have characteristics similar to those of plants and animals, which makes them difficult to classify and, therefore, are called connecting links between plants and animals.

Golden-brown algae and Diatoms (Chrysophyta)

Examples: Ochromonas sp., Chrysosaccus sp.

  • Chrysophyta includes single-celled algae in which chloroplasts contain large amounts of fucoxanthin pigment, giving the algae their brown color.
  • These are flagellated, with one tinsel-like flagellum and a second whiplash-like flagellum, which can be reduced to a short stub.
  • Resting cysts or spores with ornamented spines are formed in Chrysophyta. The cyst walls contain silica.
  • Chrysophytes are found mainly in low-calcium freshwater habitats.

Fire algae (Pyrrophyta)

Examples: Pfiesteria piscicida, Gonyaulax catenella, Noctiluca scintillans, Chilomonas sp., Goniomonas sp

  • Fire algae are single-celled algae commonly found in the oceans and some freshwater sources that use flagella to move.
  • They are divided into two classes: dinoflagellates and cryptomonads.
  • Dinoflagellates can cause a phenomenon known as red tide, in which the ocean appears red due to its high abundance. Like some fungi, some Pyrrophyta species are bioluminescent. At night, they make the ocean seem a flame. Dinoflagellates are also toxic because they produce a neurotoxin that can alter the proper functioning of muscles in humans and other organisms.
  • Cryptomonads are similar to dinoflagellates and can also produce harmful algal blooms, giving the water a red or dark brown appearance.

Red algae (Rhodoph yta)

Example Gelidium, Gracilaria, Porphyra, Palmaria, Euchema

  • Red algae are commonly found in tropical marine areas.
  • Unlike other algae, these eukaryotic cells lack flagella and centrioles.
  • It grows on a solid surface, including a tropical reef or attached to other algae.
  • The cell wall of Red algae is made up of cellulose and many different types of carbohydrates.
  • These algae reproduce asexually by monospores (walled spherical cells without flagella) that are carried by streams until germination.
  • Red algae also reproduce sexually and undergo alternation of generations.

Yellow-green algae (Xanthophyta)

Examples: Vaucheria, Botrydium, Heterococcus,

  • They are single-celled organisms with cellulose and silica cell walls and contain one or two flagella for movement.
  • Its chloroplasts do not have a certain pigment, which gives them a lighter color.
  • Yellow-green algae generally live in freshwater but can be found in saltwater and wet soils.

Brown algae (Phaeophyta)

Examples: Kelp (Laminariales), Bladderwrack (Fucus vesiculosus), Sargassum vulgare

Glossary of Terms

Algae (singular: alga): Algae is an informal term for a very diverse and large group of photosynthetic organisms that may not always be related, which is why they are considered polyphyletic.

The organisms included in this group are unicellular microalgae genera, including the diatoms and Chlorella and multicellular forms, such as the giant kelp and a large brown alga that can grow up to over 160 feet in length.

Most are autotrophic and aquatic, and they lack a lot of the distinct tissue and cell types, including xylem, stomata, and phloem – all of which are ingredients found in land plants.

Seaweeds are the most complex and the largest type of algae, and the most complex type of freshwater algae is a division of green algae called Charophyta.

Amoeboid: This term is a version of the word amoeba, which refers to an organism that can change its shape, mainly by retracting and extending pseudopods.

Amoebae are not a single taxonomic group but instead, they are found in every main lineage of eukaryotic organisms. Microbiologists often use the terms “amoeboid” and “amoebae” interchangeably, and they include many well-known species, including a type of intestinal parasite.

Ciliate: Ciliates are protozoans that have hair-like organelles called cilia, which are structurally identical to eukaryotic flagella, yet they are generally shorter and are in much larger numbers.

They also have an undulating pattern that is a little different than flagella. Cilia occur in all members of this group and can be utilized for feeding, crawling, attachment, and even sensation.

With cilia, the organism can grab food, move around, and much more. Today there are more than 5,500 species, and they can be found in both salt-water and freshwater oceans and lakes. Ciliates are also the most specialized of the protozoans and have many different organelles that perform certain processes.

Flagellate: This term relates to organisms that have a flagellum, which is a mobile, very long, whip-like appendage that appears from a basal body at the surface of a cell.

The appendages serve as a locomotor organelle, and in eukaryotic cells, the flagella contain nine separate pairs of microtubules that are arranged around a central pair. In bacteria, their strands are tightly wound and called flagellin.

The word comes from the Latin word flagellum, which means whip. Flagella are organelles that are defined by their function rather than their structure, and the main role of the flagellum is movement however, it is often used as a sensory organelle and is even sensitive to temperatures and chemicals outside of the cell.

Kelp: Kelp is a large brown algae seaweeds that are part of the order Laminariales. There are approximately 30 different types, and they all grow in shallow oceans in areas known as underwater forests. It is thought by some that kelp has been around five to twenty-three million years.

Kelp needs water that is rich in nutrients if the temperature of the water is between 42 and 57 degrees Fahrenheit. Growing up to 1.5 feet per day, they are known for their high growth rate, and they can even reach up to more than 260 feet in length.

Protozoa (singular: protozoan): Protozoa are single-celled eukaryotes and can be either parasitic or free-living, which means it feeds on organic matter that includes organic tissues and debris, as well as other microorganisms.

Protozoa historically have been known as one-celled animals thanks to their animal-like behaviors, which include predation and motility.

They also lack a cell wall, such as the ones found in many algae and in plants. The traditional practice of grouping protozoa with animals no longer is in existence, but the term is still sometimes used as a way to loosely identify single-celled organisms that feed by heterotrophy and move independently.

Slime Mold: Slime mold is an informal name used to identify numerous types of unrelated eukaryotic organisms that live freely as single cells but which aggregate together in order to form multicellular reproductive structures.

Formerly classified as fungi, slime mold is no longer considered part of that kingdom. There are approximately 500 species of primitive organisms that contain true nuclei and resemble both fungi and protozoan protists.

Sporozoa (singular: sporozoan): Sporozoa are a large class of non-motile, strictly parasitic protozoans with a complex life cycle that usually involves both sexual and asexual generations, often in various hosts.

The class also includes important pathogens that include babesias and parasites. Sporozoa are parasitic, spore-forming protozoan and include many different species.

One of these species is known as plasmodia, which is the organism that causes malaria. The mature forms do not have external organs that give it some locomotive capabilities, and some of the most common, well-known forms include Toxoplasma, Microsporidia, Plasmodium, Isospora, and Cryptosporidium.

Water Mold: Belonging to a group known as oomycetes, water molds look like other fungi thanks to their branched filaments and form spores. The water molds, however, have cellulose in their walls, even though other fungi have chitin. Oomycetes have a complicated reproductive cycle that includes zoospores, which bear flagella.

Some water molds are actually parasites of fish, while others can cause disease in plants such as potatoes, grapes, and even tobacco. Water molds are microscopic and reproduce both sexually and asexually.

They thrive under high-humidity conditions and continuous running water, and they are tiny and absorptive in nature. They also have a thallus or body, that is composed of mycelia, which is a tube-like vegetative body.

Fungus-like Protists

Fungus-like protists share many features with fungi. Like fungi, they are heterotrophs, meaning they must obtain food outside themselves. They also have cell walls and reproduce by forming spores, just like fungi.

Two major types of fungus-like protists are slime molds and water molds.

Slime Molds
Slime molds usually measure about one or two centimeters, but a few slime molds are as big as several meters. They often have bright colors, such as a vibrant yellow.

Water Molds
Water molds mostly live in water or moist soil. They can be parasites of plants and animals, getting their nutrients from these organisms and also from decaying organisms. They are a common problem for farmers since they cause a variety of plant diseases.

Slime molds are fungus-like protists that grow as slimy masses on decaying matter. They are commonly found on items such as rotting logs.
Water molds are fungus-like protists present in moist soil and surface water they live as parasites or on decaying organisms.

Watch the video: Introduction to Protozoa. Microorganisms. Biology. Dont Memorise (February 2023).