Biology: Reproduction, Biodiversity and Ecosystem Dynamics

What are the two modes of reproduction?

Sexual reproduction and asexual reproduction.

What is asexual reproduction?

Reproduction involving one parent that usually produces genetically identical offspring.

What is a clone?

An organism or cell genetically identical to another, apart from mutations.

What is binary fission?

Cell division in which one cell divides to produce two daughter cells.

How do prokaryotes reproduce asexually?

By binary fission.

How do unicellular eukaryotes reproduce asexually?

By binary fission involving mitosis.

What is mitosis?

Cell division that produces two genetically similar daughter cells with the same chromosome number as the parent cell.

What is budding?

A new organism develops as an outgrowth of the parent.

What is parthenogenesis?

The development of offspring from an unfertilised egg.

How do some fungi reproduce asexually?

By producing spores that can grow into new organisms.

What are runners?

Horizontal stems growing along the soil surface that form new plants at nodes.

What are rhizomes?

Horizontal underground stems that produce shoots and roots.

What are tubers?

Swollen underground storage structures containing buds that can grow into new shoots.

How do plant cuttings produce new plants?

A piece of a parent plant develops roots and shoots under suitable conditions.

What is artificial vegetative propagation?

Using plant parts or tissue culture to produce new plants asexually.

What are three advantages of asexual reproduction?

Only one parent is required; it is generally fast and energy-efficient; many offspring can be produced rapidly.

What are two disadvantages of asexual reproduction?

Little genetic variation between offspring; rapid population growth can increase competition for limited resources.

Why is asexual reproduction effective in stable environments?

Well-adapted parents can produce similar offspring that are also suited to the stable conditions.

Why can asexual reproduction cause exponential population growth?

Individuals can reproduce rapidly without needing to find a mate when conditions are favourable.

What is sexual reproduction?

Reproduction involving the fusion of gametes, usually producing genetically varied offspring.

Why does sexual reproduction generally have a higher energy cost?

Energy may be required to produce gametes, find mates, court and achieve fertilisation.

What is fertilisation?

The fusion of gamete nuclei to form a zygote.

What is internal fertilisation?

Fertilisation that occurs inside the female reproductive tract.

What is external fertilisation?

Fertilisation that occurs outside the body, commonly in water.

What is crossing over?

The exchange of DNA between non-sister chromatids of homologous chromosomes during prophase I of meiosis.

How does crossing over increase genetic variation?

It produces chromosomes with new combinations of alleles.

What is independent assortment?

The random orientation and separation of homologous chromosome pairs during meiosis I.

How does independent assortment increase genetic variation?

It creates gametes containing different combinations of maternal and paternal chromosomes.

What is genetic variation?

Differences in genetic information between individuals.

What is the major advantage of sexual reproduction?

It increases genetic diversity, potentially improving a population's ability to survive environmental change.

How does genetic variation support natural selection?

Individuals with advantageous heritable variations tend to survive and reproduce more, increasing the frequency of those alleles over generations.

Does sexual reproduction guarantee survival during environmental change?

No. Survival depends on the available variation and the nature and speed of environmental change.

Compare the genetic outcomes of sexual and asexual reproduction.

Asexual reproduction usually produces genetically similar offspring; sexual reproduction produces genetically varied offspring.

What is plant tissue culture?

Growing plant cells or tissues under controlled conditions on a nutrient medium to produce new plants.

Why are cloned plants genetically similar?

They originate from the same parent tissue and are produced through mitotic cell division.

What are the two main artificial cloning techniques used for mammals?

Embryo splitting and somatic cell nuclear transfer (SCNT).

What is embryo splitting?

Dividing cells of an early embryo in vitro so separate groups can develop into genetically very similar embryos.

What does in vitro mean?

A process carried out outside a living organism under controlled conditions.

What is somatic cell nuclear transfer (SCNT)?

Transferring a nucleus from a somatic cell into an egg cell whose own nucleus has been removed.

Outline the basic steps of SCNT.

Remove the egg nucleus; transfer a somatic cell nucleus; stimulate cell division; allow embryo development; transfer the embryo to a surrogate where applicable.

How does SCNT differ from embryo splitting?

SCNT uses a nucleus from a somatic cell and an enucleated egg; embryo splitting divides cells of an early embryo.

What are two problems associated with mammalian somatic cell cloning?

Low success rates and an increased risk of developmental abnormalities.

Why can cloning be considered a form of asexual reproduction?

It can produce offspring without the usual fusion of gametes from two parents.

What is the legal position on human cloning in Australia?

Australian legislation prohibits human cloning practices, including reproductive human cloning.

What is biodiversity?

The variety of living organisms, including genetic, species and ecosystem diversity.

What is genetic diversity?

Variation in genetic information, including alleles, within and between populations.

What is species diversity?

The variety of species in an area and their relative abundance.

What is ecosystem diversity?

The variety of ecosystems, habitats and ecological communities in a region.

What is an allele?

An alternative version of a gene.

Why is genetic diversity important?

It increases the chance that some individuals possess heritable traits suited to changed conditions.

How can chance events reduce biodiversity?

Natural disasters and other random events can eliminate individuals or populations and remove alleles.

What is a gene pool?

All the alleles present in a population at a particular time.

How can a small population lose genetic diversity?

Genetic drift and random events can cause alleles to disappear.

How are genetic diversity and species survival connected?

Greater genetic diversity can increase the likelihood that some individuals survive environmental change, but does not guarantee survival.

What is a tolerance range?

The range of environmental conditions in which an organism can survive and reproduce successfully.

How can humans extend their tolerance range?

Using technology such as heating, cooling, protective clothing and life-support systems.

What is an adaptation?

A characteristic that enhances an organism's ability to survive and reproduce in its environment.

What is a structural adaptation?

A physical feature that helps an organism survive, such as thick fur or plant spines.

What is a physiological adaptation?

An internal functional process that helps an organism survive, such as producing concentrated urine.

What is a behavioural adaptation?

An action that improves survival, such as being active at night.

Why do desert animals need water-conservation adaptations?

Water is scarce, and high temperatures can increase water loss.

How does nocturnal behaviour help desert animals?

It allows them to avoid daytime heat, reducing heat stress and often water loss.

How does burrowing help desert animals?

It provides shelter and can offer cooler, more humid conditions.

How does concentrated urine conserve water?

The kidneys reabsorb more water, reducing water loss in urine.

How can dry faeces conserve water?

More water is absorbed from the digestive tract before waste is eliminated.

What is dormancy?

A period of reduced activity and metabolism that helps an organism survive unfavourable conditions.

How can animal movement help during drought?

Animals may move to areas with more water, food or suitable conditions.

How can drought-resistant life stages help a species survive?

Resistant eggs, seeds or other stages persist through unfavourable conditions until conditions improve.

What are the three major vegetation types of arid and semi-arid inland Australia?

Hummock grasslands, acacia shrublands and chenopod shrublands.

What is transpiration?

The loss of water vapour from a plant, mainly through leaf stomata.

What are stomata?

Small pores in plant surfaces that regulate gas exchange and water vapour loss.

How does reduced leaf area help desert plants?

It reduces the surface area available for water loss.

How does a thick waxy cuticle help desert plants?

It reduces evaporation from the plant surface.

How does stomatal closure help plants?

It reduces water loss through transpiration but also limits carbon dioxide uptake.

What are ephemeral plants?

Plants that complete their life cycle rapidly when suitable conditions occur.

How do drought-resistant seeds help ephemeral plants?

They remain dormant during dry periods and germinate when conditions become suitable.

What is a mulga?

An acacia, commonly Acacia aneura, adapted to arid Australian environments.

How can mulga adaptations help conserve water?

Small leaves or leaf-like structures and suitable root systems help reduce water loss and access available water.

What are chenopod shrublands?

Vegetation communities dominated by chenopods, including many saltbushes, often in dry and saline environments.

How can saltbushes survive salty soils?

Salt tolerance, salt management and water-regulation mechanisms help them function in saline conditions.

What are hummock grasslands?

Grasslands dominated by hummock-forming grasses, especially spinifex grasses.

How can spinifex grasses survive dry conditions?

Their growth form, leaf characteristics and root systems help capture water and limit water loss.

How do insulating layers help animals in cold environments?

Fur, feathers or fat reduce heat transfer from the body to the surroundings.

What are antifreeze compounds?

Substances that reduce the formation or growth of ice crystals in an organism's tissues or fluids.

What is countercurrent exchange?

A system in which fluids flow in opposite directions, allowing efficient heat transfer.

How does countercurrent exchange conserve heat?

Warm blood transfers heat to cooler blood returning to the body, reducing heat loss at extremities.

How can plants survive below 0 degrees Celsius?

Cold-tolerant plants regulate solute concentrations, cell membrane flexibility and ice formation to limit cellular damage.

What is an ecosystem?

A living community, its non-living physical surroundings and the interactions within and between them.

What is the most complex level of biological organisation in these notes?

The ecosystem.

What is a population?

A group of organisms of the same species living in the same area at the same time.

What is a community?

All the populations of different species living and interacting in an area.

What is a biotic factor?

A living component or biological influence in an ecosystem.

What is an abiotic factor?

A non-living environmental factor such as temperature, light, water availability or salinity.

What is a keystone species?

A species with a disproportionately large effect on its ecosystem relative to its abundance or biomass.

Why can removing a keystone species have major effects?

It can disrupt food webs and change the abundance and distribution of other species.

Why does an ecosystem need a continual energy input?

Energy flows through organisms and is eventually dissipated as heat, so it must be replenished, usually by sunlight.

What are the three major functional groups in an ecosystem?

Producers, consumers and decomposers.

What is a producer?

An organism that makes organic compounds from inorganic substances, usually using sunlight through photosynthesis.

What is a consumer?

An organism that obtains energy and nutrients by feeding on other organisms or organic matter.

What is a decomposer?

An organism, such as a fungus or bacterium, that breaks down dead organic matter and waste.