Key Hominin Species and Evolutionary Events

These flashcards cover key terms and concepts related to hominin species, critical evolutionary events, and important biological principles discussed in the lecture.

Sahelanthropus tchadensis

Oldest known member of the human lineage, approximately 7-6 million years ago.

Ardipithecus ramidus

An early bipedal hominin that lived around 4.4 million years ago.

Australopithecus afarensis

Known for the 'first family', lived between 3.8 and 2.9 million years ago.

Genus Homo

Emerges around 2 million years ago, includes species like Homo heidelbergensis and Homo neanderthalensis.

Homo sapiens

Appeared in Africa about 300,000 years ago; modern behavior developed approximately 50,000 years ago.

Cambrian Explosion

A rapid increase in biodiversity that occurred around 541 million years ago.

Mesozoic Era

Known as the age of reptiles, including dinosaurs.

Cretaceous-Tertiary Extinction

Event leading to the extinction of dinosaurs and the rise of mammals.

Human Evolution

Divergence from chimpanzees occurred approximately 6-8 million years ago.

Allopatric speciation

A form of speciation that occurs when populations are geographically separated.

Sympatric speciation

Speciation that occurs without geographic separation, often through reproductive isolation.

Distinction between Allopatric and Sympatric Speciation

Allopatric speciation occurs when populations are geographically separated, leading to reproductive isolation. Sympatric speciation occurs within the same geographic area, often driven by reproductive isolation mechanisms like polyploidy or habitat differentiation.

Stabilizing selection

Natural selection that favors average individuals in a population, reducing variation. An example is human birth weight, where intermediate weights have higher survival rates compared to very low or very high birth weights.

Genetic drift

Random changes in allele frequencies in a population. It is more significant in small populations because random fluctuations have a greater proportional effect on allele frequencies, potentially leading to faster loss or fixation of alleles.

Synapomorphies

Shared derived characteristics that indicate a common ancestor, crucial for grouping taxa in phylogenetic analysis and constructing phylogenetic trees to show evolutionary relationships.

Homologous traits

Traits that are similar due to shared ancestry.

Analogous traits

Traits that are similar due to convergent evolution, not shared ancestry.

Distinction between Homologous and Analogous Traits

Homologous traits are similar due to shared ancestry (e.g., the pentadactyl limb structure in vertebrates), while analogous traits are similar due to convergent evolution from similar environmental pressures, not shared ancestry (e.g., the wings of birds and insects).

Phylogenetic Trees

Diagrams that represent evolutionary relationships and the history of species.

What is evolution?

The change in genetic and phenotypic variation within a population over time.

What key factors drive evolution?

Mutation, Gene Flow, Non-random Mating, Genetic Drift, and Natural Selection.

What is the role of mutation in evolution?

It is the source of new alleles, creating new genetic variation.

What is gene flow (migration)?

The movement of alleles between populations, which tends to reduce genetic differences.

What is non-random mating in evolution?

Occurs when individuals choose mates based on specific traits, often leading to sexual selection.

Define natural selection.

The process where individuals with certain advantageous traits are more likely to survive and reproduce, leading to those traits becoming more common in the population.

Who were Charles Darwin and Alfred Russel Wallace?

Key figures who independently developed the theory of natural selection.

What is directional selection?

A pattern of natural selection where one extreme phenotype is favored, shifting the population's trait distribution towards that extreme.

What is disruptive selection?

A pattern of natural selection where two extreme phenotypes are favored over intermediate ones, increasing variation within the population.

What is speciation?

The evolutionary process by which populations evolve to become distinct species.