Selection Pressures
An environmental factor (abiotic or biotic) that affects an organism's ability to survive and reproduce.
What is a selection pressure?
A physical characteristic or anatomical feature of an organism's body that enhances survival.
What is a structural adaptation?
Small-scale evolutionary changes in allele frequencies within a single population over a short period.
What is microevolution?
When closely related species evolve distinct traits because they face different environmental selection pressures.
What is divergent evolution?
The study of the geographic distribution of organisms, showing that species split from common ancestors as landmasses drifted apart.
What is biogeography?
Temperature, water availability, and light intensity are examples of this type of selection pressure.
What are abiotic pressures?
The internal bodily process or chemical reaction that allows desert mammals to produce highly concentrated urine.
What is a physiological adaptation?
Major evolutionary transitions that result in the formation of entirely new species over vast geologic time scales.
What is macroevolution?
When unrelated species evolve similar traits because they occupy similar environments (e.g., sharks and dolphins).
What is convergent evolution?
Comparing identical amino acid sequences in proteins like cytochrome c across different species falls under this line of evidence.
What is biochemistry?
Predators, diseases, and competitors are examples of this type of selection pressure.
What are biotic pressures?
An action or choice made by an organism, such as a desert lizard burrowing to avoid midday heat.
What is a behavioural adaptation?
The fundamental mechanism of evolution where organisms with favorable traits are more likely to survive and reproduce.
What is natural selection?
Darwin noticed this famous group of birds diversified into many different species across the Galápagos Islands to exploit different food sources.
What are Darwin's finches?
The study of structural similarities and differences between species to establish evolutionary pathways.
What is comparative anatomy?
The invasive front of this animal in Australia has rapidly evolved longer legs due to spatial sorting pressures.
What is the Cane Toad?
Deciduous trees dropping their leaves in winter to conserve water is an example of this specific type of adaptation.
What is a physiological adaptation?
The fossil record of this modern mammal shows a clear macroevolutionary transition from a small forest-dwelling creature with four toes to a large open-plains runner.
What is the horse?
Structures that serve a similar function but did not evolve from a common ancestor, like a bird's wing and a butterfly's wing.
What are analogous structures?
This modern, ongoing example of natural selection is driven by the human pressure of overusing medical treatments.
What is antibiotic resistance in bacteria?
This introduced biological control successfully targeted the invasive Prickly Pear cactus.
What is the Cactoblastis moth?
This type of specialized desert plant features structural adaptations like thick waxy cuticles and sunken stomata.
What is a xerophyte?
This macroevolutionary theory states that evolutionary history consists of long periods of stasis interrupted by brief bursts of rapid change.
What is Punctuated Equilibrium?
Structures in different species that share a common anatomical plan (like the pentadactyl limb), indicating common ancestry despite different functions.
What are homologous structures?
The observation that early vertebrate embryos (like fish, chicks, and humans) all possess gill slits and tails highlights this line of evidence.
What is comparative embryology?