EVOLUTION

Lamarck’s theory

Organisms acquire traits during their lifetime through use/disuse, which are then passed to offspring.

Darwin’s theory

Evolution occurs by Natural Selection; organisms with advantageous traits survive and reproduce more successfully.

Population

A group of individuals of the same species living in the same location.

Gene pool

All the genes/alleles present in a population.

Allele frequency

The proportion or percentage of a specific allele in a gene pool.

Factors causing allele frequency change

Natural selection, gene flow (migration), genetic drift (chance events).

Fitness

The phenotype that provides the greatest advantage in survival and reproduction.

Selection pressure/agent

An environmental factor that affects an organism’s reproductive success.

Reproductive success

Organisms with advantageous alleles survive, reproduce, and increase allele frequency in the population.

Natural Selection

Individuals with advantageous phenotypes survive longer and reproduce more, shifting the gene pool toward those traits.

Adaptations from natural selection

Changes that improve survival, including structural, behavioural, and physiological adaptations.

Peppered moth example

Dark moths increased in polluted environments due to camouflage advantage, illustrating natural selection.

Gene flow

The movement of alleles from one population to another, altering allele frequencies.

Genetic drift

Random change in allele frequencies, especially in small populations, not based on fitness.

Founder effect

A new population is formed from a few individuals, leading to reduced genetic variation.

Population bottleneck

A drastic reduction in population size that decreases genetic diversity and can lead to extinction.

Artificial selection

Humans select parents with desired traits to produce offspring.

Artificial selection effects

Can increase frequency of desired alleles but may reduce genetic diversity and fitness.

Speciation

Formation of new species through geographic isolation, different selection pressures, and reproductive isolation.

Reproductive isolation

Prevents interbreeding through physical barriers, courtship rituals, breeding seasons, and mechanical incompatibility.

Species

Organisms that can produce fertile offspring.

Hybrid animals

Offspring of different species; often sterile or unfit.

Race/breed/subspecies

Genetic variations within the same species capable of interbreeding.

Biogeography

Study of species distribution, explaining evolution via geographic isolation.

Ratite birds example

Similar flightless birds on different continents suggest common ancestry and continental drift.

DNA and protein similarities

Similar DNA/amino acid sequences indicate closer relatedness among organisms.

Embryology

Similarities in embryos suggest shared ancestry among different species.

Comparative morphology

Study of structures to determine the relatedness of organisms.

Homologous structures

Same structure, different function, indicating divergent evolution.

Vestigial structures

Reduced or non-functional remnants of structures from ancestors.

Analogous structures

Different structures with the same function, indicative of convergent evolution.

Fossil

Preserved remains or traces of past life.

Fossilisation requirements

Rapid burial, sediment layers, mineralisation, or preservation are needed for fossil formation.

Strata

Layers of rock, with older fossils found in lower layers.

Index fossils features

Common, widespread, and short-lived fossils that help date rock layers.

Transitional fossils

Show features of both ancestral and modern species.

Hominin

Humans and their extinct ancestors.

Skull features for age

Cranial capacity, eyebrow ridge size, teeth size, foramen magnum position.

Bipedalism traits

Inferior foramen magnum, S-shaped spine, shorter arms, broader pelvis.

Australopithecus afarensis (Lucy)

Early hominin with a 400mL brain, bipedal, lived 3.9–2.9 million years ago.

Homo habilis (Twiggy)

Early hominin with a 640mL brain, known for tool use, lived 2.4–1.4 million years ago.

Homo erectus

Early hominin with a 1000mL brain; used fire and migrated from Africa.

Human evolutionary trends

Trends include larger brain size, shorter arms, flatter face, and more central foramen magnum.

Migration out of Africa

Homo sapiens left Africa 50,000–60,000 years ago, reaching Australia via Sahul.

how a mold or cast fossil is formed.

1. The animal is covered quickly by sediments

2. Over time the bone decomposes leaving a gap (mold)

3. Minerals fill the mold and solidify forming a cast of the bones) fossil

Trace fossil

evidence that life existed in the past

Index fossil

used to determine the age of other fossils