Evolution and Natural Selection

Comprehensive practice flashcards reviewing evidence for evolution, mechanisms of natural and artificial selection, comparative anatomy, speciation, and evolutionary theories from Darwin and Lamarck.

What are the primary areas of study that provide evidence for evolution?

Fossils (remains of extinct species), living fossils, comparative anatomy, analysing vertebrate embryos, comparing amino acid sequences in proteins, comparing species' DNA, and biogeography.

How does comparative anatomy distinguish between homologous and analogous structures?

Homologous structures share similar anatomical structures but have different functions, arising via divergent evolution. Analogous structures perform the same function with different anatomical structures, arising via convergent evolution.

What evolutionary pattern is shown in this diagram featuring the fin of a shark, wing of a penguin, and flipper of a dolphin?

Analogous structures resulting from convergent evolution, where unrelated species evolve similar functional traits due to occupying similar environments.

What is parallel evolution?

An evolutionary pattern where two species arise from a common ancestor and develop in the same way because their environments are similar.

What evidence do early vertebrate embryos provide regarding common ancestry?

They display homologous structures during early development—such as gill-slits and tails—that are not visible in the adult forms of all species, indicating a shared common ancestor.

What is natural selection and how does it act as the mechanism of evolution?

It is the process whereby individuals with the best phenotype survive and pass on their genes, causing the most advantageous genotypes and alleles to become more common in the population over time.

What four conditions are necessary for natural selection to occur?

1. Variation (heritable phenotypic differences caused by mutation)
2. Differential Survival (selective pressures preventing some individuals from surviving or reproducing)
3. Genetic Inheritance (passing selective advantages to the next generation)
4. Frequency (an increase in the proportion of individuals with the advantageous traits over generations).

What historic milestone is captured in this sketch from Charles Darwin's notebook?

The very first 'evolutionary tree' diagram, demonstrating Darwin's concept that a single ancestral species could diverge into multiple distinct species.

How is a biological species defined?

A group of organisms that can interbreed with one another and produce viable, fertile offspring.

What role does isolation play in the process of speciation?

Isolation prevents populations from reproducing with one another, allowing them to accumulate genetic differences through natural selection until they can no longer interbreed.

What was Jean-Baptiste Lamarck's 1809 theory of evolution, and why was it disproved?

Lamarck proposed Evolution by Transformation (use and disuse), where habitual use developed features and disuse led to atrophy, with acquired traits passed to offspring. It was disproved because acquired physical modifications (such as cutting off a rat's tail) are not inherited genetically.

How did Charles Darwin's 1859 theory explain the evolution of long-necked giraffes differently from Lamarck's theory?

Lamarck claimed giraffes stretched their necks over lifetimes to reach higher leaves, whereas Darwin explained that long-necked giraffes were born with random variations giving them a competitive advantage to survive and reproduce more offspring.

How did the 14 species of Darwin's finches on the Galapagos Islands evolve?

They evolved from a single ancestral finch species via natural selection, with beak shapes adapting over generations to suit the specific food sources available on each island.

Based on this diagram, how do allopatric speciation and sympatric speciation differ?

Allopatric speciation occurs when a physical geographical barrier divides an ancestral population, whereas sympatric speciation occurs within the same geographical location without a physical barrier (often via reproductive isolation).

What is artificial selection?

The practice where human breeders deliberately select and propagate small variations in domestic animals or plants to modify and improve traits across successive generations.

What distinct domestic vegetables were developed from the single wild mustard plant through artificial selection?

Broccoli (suppression of flower development), cabbage (suppression of internode length), kale (enlargement of leaves), cauliflower (sterility of flowers), and kohlrabi (enhancement of lateral meristems).

What common ancestor gave rise to diverse modern dog breeds across Europe, North America, China, and India through artificial selection?

The gray wolf.

What is biodiversity?

The range of life forms within a given species, ecosystem, biome, or an entire planet.