Reproduction
Differences between male and female sexes in sexual reproduction
D3. 1.3
Compare motility, size, energy reserves and production rate of male and female gametes of plants and animals
Male and female gametes vary significantly in their production rate, size, and energy reserves.
Note that not all male gametes are called sperm (plants: pollen) and not all female gametes are eggs (plants: ovum)*.
For some comparison using humans as an example: In a single ejaculate, a male produces between 1.5 to 5 billion sperm (on average). Females, on the other hand, will typically ovulate around 400 to 500 eggs throughout their fertile lifetime*.
Comparing male to female gametes:
Anatomy of the human male and female reproductive systems
D3. 1.4
Annotate diagrams of the male and female reproductive systems to show names of structures and their functions
Male Reproductive System
Annotated diagram of the male reproductive system to show names of structures and their functions
Testis
Bladder
Vas Deferens
Prostate Gland
Seminal Vesicle
Epididymis
Urethra
Bladder
Seminal Vesicle
Erectile Tissue
Urethra
Testis
Epididymis
Penis
Vas Deferens
Prostate Gland
Ureter
Male Reproductive Organs
Structure | Function |
Testes | Produces sperm and male sex hormones (testosterone) |
Epididymis | Site where sperm matures and develops capacity to swim |
Vas Deferens | Carries sperm from the testes to the urethra |
Seminal Vesicle | Secretes fructose (for sperm nutrition) and prostaglandins |
Prostate Gland | Secretes an alkaline fluid to neutralise vaginal acids |
Urethra | Carries sperm to the outside of the body (via the penis) |
Female Reproductive System
Annotated diagram of the female reproductive system to show names of structures and their functions
Bladder
Vagina
Cervix
Uterus
Urethra
Fallopian Tube (oviduct)
Ovary
Endometrium
Fallopian Tube
(Oviduct)
Vagina
Ovary
Fimbriae
Uterus
Female Reproductive Organs
Structure | Function |
Ovary | The reproductive organ where eggs (ova) are produced |
Fimbriae | A fringe of tissue that sweeps an oocyte into the oviduct |
Oviduct | The tube where an ovum passes to the uterus (fallopian tube) |
Uterus | The organ where a fertilised egg will implant and develop |
Endometrium | A mucous membrane lining the uterus (shed via menstruation) |
Vagina | Passage leading to the uterus via which a penis can enter |
Changes during the ovarian and uterine cycles and their hormonal regulation*
D3. 1.5
Distinguish between ovarian cycle and uterine cycles
Refers to specific changes in the ovaries that occur over the course of roughly 28 days.
Ovarian cycle
Uterine cycle
AKA the endometrial cycle, refers to the changes specifically in the endometrium (the lining of the uterus) in response to hormonal fluctuations.
Menstruation is part of this cycle.
Distinguish between ovarian cycle, uterine cycle and menstrual cycle
The menstrual cycle describes recurring changes that occur within the female reproductive system to make pregnancy possible.
Note: menstrual cycle is an overarching term that encompasses the ovarian cycle and the uterine cycle.
The menstrual cycle
Each menstrual cycle lasts roughly one month (~28 days) and begins at puberty (menarche) before ending with menopause.
State the source and location of action of hormones in the menstrual cycle:
There are two key groups of hormones which control and coordinate the menstrual cycle: pituitary and ovarian hormones.
Pituitary hormones (from the brain)
Ovarian hormones (...from the ovaries)
Side question: Do males produce FSH and LH?**
**Follow the arrows!!
What exactly is a follicle?
Explain the feedback loops that regulate the menstrual cycle
There are four key events that comprise a typical menstrual cycle:
If fertilisation occurs, the developing embryo will implant in the endometrium and release hormones to sustain the corpus luteum.
Menstruation
If fertilisation doesn’t occur, the corpus luteum eventually degenerates (forming a corpus albicans after ~ 2 weeks).
Menstruation
The endometrial layer is eliminated from the body as menstrual blood (i.e. a woman’s period).
Menstruation
Fertilization in humans
D3. 1.6
Describe the process of fertilization in humans
The process of fertilization in humans involves a number of key processes, including:
Occurs after ejaculation, when chemicals released by the uterus dissolve the sperm’s cholesterol coat.
Capacitation
Acrosome Reaction
Dissolution of nuclear membranes
(This ensures only the sperm's genetic material contributes to the formation of the zygote.)
Outline the events of joint mitosis following fertilization
The last stage is joint mitosis, often referred to as “the first mitotic division”.
All the genetic material from the sperm and egg (in the form of condensed chromosomes) combine and undergo the first cell division to form a diploid (2n) zygote.
Use of hormones in in vitro fertilization (IVF) treatment
D3. 1.7
Define in vitro fertilization (IVF)
In vitro fertilisation (IVF) refers to fertilisation that occurs outside of the body (in vitro = "in glass").
It involves using drugs to suspend normal ovulation (down regulation), before using hormone treatments to collect multiple eggs (superovulation).
It’s the 1970s. Millions of couples want babies, but can’t get pregnant.
But science is cool. And helpful.
(In pairs) Propose a short, bullet-point procedure to pitch the first IVF treatment to get the first of these couples the first IVF baby.
DO IT ON PAPER!
We’re then going to apply our previous knowledge to poke holes in your suggested procedure.
Outline the process of in vitro fertilisation including down-regulation, superovulation, harvesting, fertilization and implantation
The following slides cover the details in 4 main steps:
Down regulation
Superovulation
Fertilization
Implantation
Drugs are used to halt the regular secretion of FSH and LH – this in turn stops the secretion of estrogen and progesterone.
By arresting the hormonal cycle, doctors can take control of the timing and quantity of egg production by the ovaries.
The drug treatment usually takes about two weeks and is typically delivered in the form of a nasal spray
Down regulation
Superovulation involves using artificial doses of hormones to develop and collect multiple eggs from the woman.
Superovulation
The patient is firstly injected with large amounts of FSH to stimulate the development of many follicles.
A large dose of hCG stimulates the follicles to mature. The eggs are then collected (via aspiration with a needle) prior to the follicles rupturing.
The extracted eggs are then incubated in the presence of a sperm sample from the male donor.
The eggs are then analysed under a microscope for successful fertilisation.
Fertilization
Approximately two weeks prior to implantation, the woman begins to take progesterone treatments to develop the endometrium.
Implantation
Multiple embryos are transferred to improve chances of successful implantation (hence twins/triplets/etc. are far more common in IVF).
Implantation
Healthy embryos are selected and transferred into the female uterus (or the uterus of a surrogate).
Differences between sexual and asexual reproduction
D3. 1.1
Life reproduces in one of two ways:
Compare sexual and asexual life cycles
Asexually
Sexually
The formation of offspring from a single parent cell(s) that are genetically identical to the parent.
Requires two different sex cells (haploid cells) from two different individuals fusing together to reproduce the first cell (diploid cell) of a new organism.
…some examples of asexual reproduction
All bacteria (prokaryotes)
Some single-celled eukaryotes (e.g. paramecia)
Plants can reproduce BOTH sexually and asexually. "Cuttings" are asexually reproduced plants.
Discuss the advantages and disadvantages of asexual reproduction
What are some advantages for organisms that reproduce asexually?
It's fast (faster than sexual reproduction, which always starts with a single cell).
It's easy - no partner needed!
(it costs time and energy to ensure sperm meets egg).
All beneficial traits will be cloned.
Discuss the advantages and disadvantages of asexual reproduction
What are some disadvantages of asexual reproduction?
No variation = diseases are easily transmitted
Fast reproduction = resources get used up too fast
No variation = offspring can't adapt to big changes in the environment
Vegetative propagation
budding
Binary fission
There are 6 methods of asexual reproduction. You’ve already studies several. List as many as you can think of:
Outline the main mechanisms of asexual reproduction
Asexual reproduction
Fragmentation
Spore formation
Parthenogenesis
Binary fission
Budding
(MORE complex stuff than binary fission)
Fragmentation
The growth of a new organism from a separated portion of a parental organism.
From the fragment, the offspring will develop to be morphologically identical to the parent.
Fragmentation is common to starfish, as well as certain species of annelid worms.
Vegetative propagation
When sections of a plant break off and grow independently. This is because all plants possess meristematic tissue which is totipotent (undifferentiated).
Virtually all types of roots and shoots are capable of vegetative propagation.
Spore formation
Some plant species form spores via an alternating cycle of generations.
A diploid plant will form a haploid spore (via meiosis) that will then germinate to form a haploid plant.
The haploid plant then produces gametes (via mitosis) which can fuse with another haploid gamete to form a diploid offspring.
Parthenogenesis (aka virgin birth)
Sexual reproduction in flowering plants
D3. 1.8
Features of an insect-pollinated flower
D3. 1.9
Draw and label an animal pollinated flower*
Flowers are the reproductive organs of angiosperms (flowering plants) and contain both male and female structures.
Most flowers possess both male and female structures (monoecious), but some may only possess one structure (dioecious).
This does mean that flowers are hermaphroditic (possess both male and female parts), and therefore can self-pollinate.
However, many plants have mechanisms to avoid self-pollination, as it reduces variation and therefore survival.
Anther – pollen producing organ of the flower (pollen is plant sperm).
Filament – slender stalk supporting the anther (makes the anther accessible to pollinators)
The male part of the flower is called the stamen and is composed of --
The female part of the flower is called the pistil (or carpel) and is composed of --
Stigma – the sticky, receptive tip of the pistil that is responsible for catching the pollen.
Style – the tube-shaped connection between the stigma and ovule (it elevates the stigma to help catch pollen).
Ovule – the structure that contains the female reproductive cells (after fertilisation, it will develop into a seed).
In addition to these reproductive structures, flowers possess a number of other support structures --
Peduncle – Stalk of the flower.
Sepal – Outer covering which protects the flower when in bud,
Petals – brightly coloured modified leaves, which function to attract pollinators.
Pollen grains
Anther
Filament
Stamen
Each pollen grain contains two sperm cells (the gametes of the plant).
Cross section of a magnified anther, showing the pollen grains.
Stigma
Style
Ovary
Ovules (inside)
Practice! See if you can identify the key reproductive parts from the flowers in this video.
Plants can reproduce in a number of different ways:
Review
Define pollination, fertilization and seed dispersal
The transfer of pollen grains from an anther (male plant structure) to a stigma (female plant structure)
Fusion of a male gamete nuclei with a female gamete nuclei to form a zygote.
Moving a seed away from the paternal plant (to prevent both parent + offspring competing for the same resources)
State the changes to the ovule and ovary that result from fertilization
Once fertilized, the ovule develops into a seed and the ovary develops into a fruit.
…side note: these are all fruits!
Methods of promoting cross-pollination
D3. 1.10
Self-incompatibility mechanisms to increase genetic variation within a species
D3. 1.11
Define cross-pollination
Cross-pollination is the process by which pollen from the anther (the male part) of one flower is transferred to the stigma (the female part) of another flower of the same species (or a closely related species).
Cross-pollination can occur through various agents such as wind, water, insects (e.g. bees and butterflies), birds, and other animals (see D3.1.12).
Outline the benefits of cross-pollination and self-incompatibility in flowering plants
Cross pollination is an essential mechanism for genetic diversity in plants:
It allows for the mixing of genetic traits from different parent plants.
…new combinations = new potential adaptations!
List methods for promoting cross-pollination in flowering plants
Several mechanisms have evolved in plants to encourage cross-pollination and self-incompatibility (resisting self-pollination):
Dioecy
Dioecious plants have individual plants are either male or female (self-pollination is not possible!).
Protandry and Protogyny
Mechanisms where a flower's male and female parts mature at different times.
Heterostyly
Plants with flowers of different lengths of stamens and pistils within the same species.
Dioecy
(dioecious plants)
In dioecious plants, the entire plant is either male, or female. Cross-pollination is necessary for reproduction because a plant cannot self-pollinate.
👈 Cannabis is a common example of a dioecious plant.
Protandry and Protogyny
In protandry (see right), the male parts mature first. In protogyny (see left), the female parts mature first*.
This off-timing reduces the chances of self-pollination.
Geranium maculatum
Heterostyly
Flowers on the same species have different styles (lengths of the pistil) and stamens*.
Define self-incompatibility
Self-incompatibility in plants is a genetic mechanism that prevents self-fertilization and promotes cross-pollination*.
Outline the mechanism that promotes self-incompatibility in flowering plants
Self-incompatibility (SI) is a complex genetic system in plants in which a plant can recognize and reject its own pollen or the pollen from genetically similar individuals.
Common self-incompatible plants include tomatoes, potatoes, and Brassica (broccoli, mustard, etc)
Self-incompatible plants avoid self-pollination via different forms of proteins produced from a gene called the S-allele.
(👇 The S-allele is located on chromosome 1 of tomato plants)
If the S-allele from a pollen grain matches the S-allele from the stigma in the female plant, the pollen will be rejected (no pollen tube will grow, hence no fertilization will take place)*.
Dispersal and germination of seeds
D3. 1.12
List mechanisms of seed dispersal
Angiosperms have evolved a variety of ways to disperse their seeds.
The structure of the seed will vary depending on the mechanism of dispersal employed by the plant.
Wind dispersal - just one of many!
List mechanisms of seed dispersal
↑ Packing a seed in a tasty fruit has the added bonus of free fertilizer (poop).
Animal dispersal (via both eating and sticking)
Water dispersal
(e.g. coconut)
Burst dispersal
(e.g. peas, "exploding cucumber")
Fire dispersal
(e.g. lodgepole pine, Banksia plants)
Define germination
Germination is the process by which a seed begins to sprout.
Describe necessary conditions for seed germination
Oxygen - for aerobic respiration (the seed requires large amounts of ATP in order to develop).
Water - to metabolically activate the seed (triggers the synthesis of gibberellin)
Temperature - For optimal function of enzymes, seeds require certain temperature conditions in order to sprout.
pH - Also for optimal function of enzymes, seeds require a suitable soil pH in order to sprout.
Outline the role of gibberellin during germination
Gibberellin (GA) is a plant hormone that regulates a wide range of processes involved in plant growth and development.
Two key functions of gibberellin:
Write five example problem questions for experiments that could test factors affecting germination
In addition to water, oxygen, etc., certain plant species may require additional conditions for germination:
Fire - some seeds will only sprout after exposure to intense heat (e.g. eucalyptus, lodgepole pine, etc).
Freezing - some seeds will only sprout after periods of intense cold (e.g. in spring, following the winter snows). Ex: cyclamen
Digestion - some seeds require prior animal digestion to erode the seed coat before the seed will sprout.
Scarification - Seeds are more likely to germinate if the seed coat is weakened from physical damage.
This obviously takes place primarily from natural causes - e.g. damage from dispersion, digestion, etc.
Scarification can be mechanical, chemical, thermal (heat OR, frost damage), and acidic (from ph).
Write five example problem questions for experiments that could test factors affecting germination
Using any of the aforementioned factors, design an experiment that would investigate how that factor affects germination. (you choose the plant!)
Sources: