Biology - Module 3 - Biological Diversity

Ecosystem

An area containing a community of living things that interact with each other and their physical (non-living) environment.

Abiotic factor

Non-living components of an environment, e.g. temperature, rainfall, pH, wind, light intensity, day length, gas availability, salinity.

Biotic factor

Living components of an ecosystem, including members of the same species and other species (plants, animals, microorganisms).

Biodiversity

The variety of living things on Earth, made up of ecosystem diversity, species diversity and genetic diversity.

Ecosystem diversity

The range of different ecosystems found on Earth / in a region.

Species diversity

The range/number of different species found in an ecosystem or community.

Genetic diversity

The range of different genes (and size of gene pool) within a species; important for the process of evolution.

Abundance

The number of individuals of a species in a specific area at a specific time.

Selection pressure

A factor in the environment that affects the survival and reproduction of individuals, favouring those with advantageous variations over others.

Biotic selection pressure

A living-factor selection pressure, e.g. competition for a mate or food availability (e.g. sexual selection causing bright colours in male birds).

Abiotic selection pressure

A non-living-factor selection pressure, e.g. water availability or climate (e.g. light availability affecting rainforest plants).

Environment

All living and non-living things in an organism's surroundings; can be aquatic or terrestrial.

Selection pressure model (variation → dominance)

Variation in population → selection pressure → death of unfavourable / survival of favourable → reproduction passes on favourable traits → dominance of the favourable trait over time.

Effect of light on organisms

Affects animal/plant behaviour and characteristics, plant root growth, leaf expansion, animal growth, colouration (camouflage), migration, circadian rhythm.

Dormancy

A temporary slowing of an organism's growth, development and activity to conserve energy (e.g. short-term daily torpor, long-term hibernation).

Effects of temperature

Affects dormancy (torpor/hibernation), and organism growth, development and activity.

Effects of weather

Affects growth, behaviour, reproduction; birds can sense pressure changes ('internal barometer') affecting flight and feeding.

Effects of water availability

Depends on rainfall, presence of fresh/salt water, glacial locking, humidity; affects growth and plant/animal structure, function and behaviour.

Role of shelter

Provides protection from weather and predators, and space for growth, development and social activity; can be biotic (tree) or abiotic (burrow).

Viscosity (aquatic vs terrestrial)

Water is more viscous than air, so aquatic organisms are more streamlined to move through it; air is less viscous.

Buoyancy (aquatic vs terrestrial)

Water provides an upthrust supporting aquatic organisms; terrestrial organisms lack this and need a skeleton or other support.

Temperature variation (aquatic vs terrestrial)

Aquatic temperature fluctuations are smaller and decrease with depth; terrestrial fluctuations are extreme (e.g. deserts 45°C day, 2°C night).

Availability of gases (aquatic vs terrestrial)

Oxygen is less available and diffuses slower in water than air; air is ~20% oxygen with faster diffusion, though oxygen decreases with altitude.

Water/ion availability (aquatic vs terrestrial)

Aquatic organisms exchange water via osmosis (saltwater organisms lose water, freshwater organisms gain water); terrestrial organisms face varying water/ion availability and risk dehydration from evaporative cooling.

Light penetration (aquatic vs terrestrial)

Light decreases with depth in water (penetrates to ~100m, depends on turbidity), restricting plants to upper layers; light intensity is high on land.

Pressure variation (aquatic vs terrestrial)

Water pressure increases with depth; air pressure decreases with altitude.

Intraspecific competition

Competition between members of the same species for a limited resource.

Interspecific competition

Competition between members of different species for a limited resource.

Predation

A relationship where a predator obtains food by killing and eating another animal (the prey), e.g. dingo and rabbit.

Allelopathy

Release of chemical substances by one species that inhibits the growth of another, e.g. Casuarina tree needles releasing acid into soil.

Parasitism (+/-)

A relationship where one species benefits and the other is harmed, e.g. tapeworm in a dog's gut.

Mutualism (+/+)

A relationship between different species where both benefit, e.g. clownfish and anemone; lichen (alga and fungus).

Commensalism (+/0)

A relationship where one species benefits and the other is neither harmed nor helped, e.g. remora fish and shark; epiphytes on trees.

Ecology

The study of interrelationships between different organisms and between organisms and their environment.

Lincoln Index formula

Population size = (n1 × n2) / n3, where n1 = total caught & marked first time, n2 = total caught second time, n3 = marked animals caught second time.

Capture-mark-recapture method

1) Capture and mark a random sample, release; 2) allow time to mix with population; 3) recapture a sample and count marked individuals; 4) use the abundance formula to estimate population size.

Percentage cover method

Uses randomly placed quadrats (e.g. 1m x 1m) to estimate percentage cover of a plant species or sessile animal; percentages from multiple quadrats are averaged to estimate cover, useful when organisms are too numerous to count individually.

Adaptation

A characteristic an organism has inherited that makes it suited to its environment, arising from random variation during reproduction; must allow survival and reproduction to be passed on.

Structural adaptation

A physical feature of how an organism is built that aids survival, e.g. penguin blubber and dense feathers, platypus webbed feet, spinifex grass thin leaves, thorny devil spikes, kangaroo tail.

Physiological adaptation

An internal process at the cellular/tissue/organ/system level that is not a choice (the body just does it), e.g. black bear lowering metabolism for hibernation, marsh crab excreting excess salt, flamingo alkaline tolerance, snail aestivation.

Behavioural adaptation

An action an organism performs (can be learned within its lifetime) to increase survival chances, e.g. redback spider's 3D web, puffer fish inflating, penguins huddling.

Echidna structural adaptations

Spiny needles for protection from predators; long tongue for eating ants/termites; females have a pouch to protect puggles.

Echidna behavioural adaptations

Curls into a ball or buries itself when scared; swims to cool off; forms an 'echidna train' during mating season.

Echidna physiological adaptations

Produces sticky saliva to coat the tongue for catching ants/termites; regulates body temperature internally to survive in almost any Australian habitat; females produce a scent to attract males.

Giraffe structural adaptations

Height to reach high food; long prehensile tongue and fleshy lips to strip leaves without injury; big heart for blood flow; four-chambered ruminant stomach; keen eyesight and hearing; spotted coat for camouflage.

Giraffe behavioural adaptations

Can run fast (56kph) for short distances; delivers a strong kick against predators; males perform 'necking' to establish dominance and reproductive access.

Giraffe physiological adaptation

A complex network of blood vessels at the base of the brain regulates blood flow when lowering the head to drink, preventing blackouts/haemorrhages; short sleep cycles keep them alert.

Venus fly trap behavioural adaptation

Trigger hairs detect prey movement (two touches needed to close, preventing false triggers); the trap seals tighter the more prey struggles, then digests the prey — an adaptation to obtain nutrients from acidic, waterlogged, nutrient-poor soils.

Niche

A specific environment/role in which an organism can survive.

Microevolution

Small-scale changes in allele frequencies within a population over a short time span (e.g. one generation), such as antibiotic resistance in bacteria or peppered moth colour change.

Macroevolution

Large-scale evolutionary change across species over long time spans, resulting in new species and higher taxonomic groups (e.g. horse evolution).

Gene pool

The total genetic information contained in the genes of all individuals in a population.

Allele frequency

The proportion of different alleles (forms of a gene) in the gene pool.

Mutation

A change in DNA sequence that introduces new alleles into a population.

Gene flow

Movement of alleles from one population to another, often through migration.

Genetic drift

Random changes in allele frequencies, often significant in small populations (e.g. bottleneck effect, founder effect).

Natural selection

The process by which individuals with advantageous traits survive and reproduce more successfully, changing allele frequencies over time.

Speciation

The process by which new species arise, e.g. allopatric, sympatric, or parapatric speciation.

Phylogeny

The evolutionary history and relationships among species or groups.

Adaptive radiation

The rapid evolution of diversely adapted species from a single common ancestor.

Extinction

The permanent loss of a species, removing its genetic contribution from the gene pool.

Punctuated equilibrium

A theory that evolution occurs in short bursts of rapid change followed by long periods of stability (equilibrium), eliminating the need for missing links in the fossil record.

Gradualism

A theory that evolutionary change occurs slowly and steadily over time through the accumulation of small changes, predicting that transitional fossil forms should exist.

Catastrophism

A sub-component of punctuated equilibrium theory: natural disasters cause sudden ecosystem changes that result in rapid evolution.

Homologous structures

Anatomical features in different species that are similar due to shared ancestry, e.g. the pentadactyl limb of vertebrates.

Convergent evolution

The process where unrelated organisms evolve similar traits (analogous structures) due to similar environments/selection pressures, e.g. streamlined bodies of sharks, dolphins, ichthyosaurs and penguins.

Divergent evolution

The process where species sharing a common ancestor evolve and accumulate differences over time, often forming new species, e.g. woolly mammoth and modern elephant from a common ancestor.

Species (biological definition)

A group of organisms that can interbreed and produce fertile offspring under natural conditions.

Isolation and speciation

When groups of the same species become isolated in different environments, differing selection pressures cause divergence; if differences become great enough, interbreeding stops and speciation occurs.

Darwin's finches

Different Galapagos finch species evolved differing beak lengths/sizes suited to different available food sources on different islands, supporting evolution by natural selection from a common ancestor.

Natural selection steps (Darwin-Wallace)

1) Variation exists within a population; 2) more offspring are produced than survive; 3) better-adapted offspring survive and reproduce ('survival of the fittest'); 4) favourable characteristics increase in the population over time, potentially forming a new species.

Sexual selection

A form of selection based on an organism's success at finding a mate.

Vestigial structure

A body part thought to be an evolutionary remnant that no longer serves its original function, e.g. human wisdom teeth, goosebumps, appendix, snake leg-like spurs.

Homologous vs analogous structures

Homologous structures are similar due to shared ancestry (divergent evolution); analogous structures are similar due to similar function/environment despite no shared ancestry (convergent evolution).

Biogeography

The study of the geographic distribution of species; isolated species (e.g. on remote islands like the Galapagos) tend to resemble species from their nearest historical land connection more than unrelated nearby species.

Comparative embryology

The study of embryonic development used to infer evolutionary relationships, e.g. shared pharyngeal slits, tails and muscle blocks across vertebrate embryos point to a common ancestor.

Comparative anatomy

Comparing body structures across species to identify homologous (shared ancestry) and vestigial (remnant) structures as evidence for evolution.

Biochemical evidence for evolution

Comparison of DNA/protein sequences across species; all living things share the same macromolecules and biochemical processes, with differences proportional to time since common ancestry (e.g. ~98.6% DNA similarity between humans and chimpanzees).

DNA-DNA hybridisation

A technique comparing nucleotide base similarity between species: DNA strands are heated to separate, then mixed with another species' DNA — more similar sequences are harder to separate, indicating closer relatedness.

Fossil evidence for evolution

Fossils establish timeframes for evolutionary change, provide transitional forms, and show biogeographical distribution consistent with evolutionary theory and continental drift; fossils only form in sedimentary rock.

Law of superposition

Younger layers of sedimentary rock sit on top of older layers, used for relative dating.

Law of original horizontality

Layers of sedimentary rock are originally deposited flat.

Law of cross-cutting relationships

Rock layers must be older than any intrusion (e.g. volcanic feature) that disturbs them.

Law of lateral continuity

Layers of rock are continuous until they meet other solid bodies or are acted on by later processes.

Index fossils

Fossils used to correlate the relative ages of rock strata from different areas.

Relative dating

Determining the age of rock layers/fossils relative to one another (not exact years), using laws like superposition and index fossils.

Absolute (isotopic) dating

Dating rocks using known half-lives of radioactive isotopes (e.g. Carbon-14, Potassium-Argon, Uranium-Lead) to give a specific age range.

Carbon-14 dating

Uses the ~5,730 year half-life of Carbon-14 to date organic materials/shells up to about 100,000-50,000 years old.

Limitations of the fossil record

Biased towards marine/aquatic organisms and organisms with hard parts; dating limitations of sedimentary rock; fossils can be lost via the rock cycle; soft-bodied fossils are hard to interpret; behaviour/physiology rarely preserved.

London Underground mosquito (Culex pipiens molestus)

A mosquito that evolved within London's underground tube tunnels from populations tracing back to the Mediterranean/Middle East; an example of relatively rapid (allopatric-style) evolutionary divergence in an isolated environment.

Anole lizard case study

Caribbean anole lizards show both convergent and divergent evolution: species occupy different vertical habitat niches (grass/bush, trunk, twig, canopy) with differing leg length and toe pad size suited to their niche, plus dewlap colour differences causing reproductive isolation between species.

Reproductive isolation

When populations of a species can no longer interbreed, often due to geographic separation or behavioural differences (e.g. mate-recognition signals like dewlap colour in anoles), leading to speciation.

Quoll and cane toad example

Quolls were captured, given a small non-lethal dose of cane toad poison, and released, creating a learned aversion so they avoid eating cane toads — an example of a technique used to help native species adapt to an invasive species.

Monotreme

An ancient group of egg-laying mammals (e.g. platypus, echidna) that diverged from the main mammal lineage roughly 165-180 million years ago.

Platypus/echidna divergence

Platypus and echidna are thought to have diverged from each other around 19-48 million years ago; platypus fossil evidence in both Australia and South America suggests it evolved before the supercontinent split.

Convergent evolution example: marsupial/placental niches

Australian marsupials (e.g. Tasmanian tiger, marsupial mole, sugar glider) evolved similar body forms/niches to unrelated placental mammals elsewhere (e.g. wolf, mole, flying squirrel) due to similar selection pressures.

Taxonomic hierarchy (general to specific)

Kingdom → Phylum → Class → Order → Family → Genus → Species (from very general to very specific classification).

Cane toad introduction to Australia

Cane toads (Rhinella marina) were introduced to Queensland in 1935 to control cane beetle pests in sugar cane crops; they failed at this task and became a major invasive species, being toxic at all life stages and lacking natural predators/controls in Australia.

Cane toad selection pressure: dispersal

At the invasion front, spatial selection favours toads that disperse fastest, so each generation at the front is made up of the fastest-dispersing individuals — an example of rapid evolution driven by abiotic and biotic selection pressures (space, competition, resources).

Cane toad evolutionary change: leg length

Toads at the invasion front have evolved significantly longer legs (and different limb proportions) than toads from long-established populations, allowing them to travel further per night; the invasion rate has increased roughly five-fold since 1935 (from ~10km/year to 50+km/year).