Evidence for Evolution, Geologic Time, and Extinction

Comprehensive review flashcards covering comparative embryology, DNA evidence, homologous and vestigial structures, fossil evidence, phylogenetic trees, the K-Pg mass extinction, and geologic time principles.

What is the geologic time scale?

A system used by Earth scientists to organize and date events in Earth's history.

According to the notes, how long is Earth's geologic time, and when did life begin?

Geologic time encompasses $4600$ million years of Earth's history, and life began $3500$ million years ago.

How is evolution defined, and what causes it to occur?

Evolution is the gradual change in a species over time, which occurs as a result of genetic variation.

What is coevolution?

When the evolution of life changes the physical nature of Earth, and those physical changes, in turn, influence the evolution of life.

How did early photosynthetic organisms trigger coevolution on Earth?

An increase in photosynthesis added more oxygen to the atmosphere, which increased rock weathering and soil nutrients, ultimately promoting the evolution of more complex, multicellular plants and animals that use oxygen for energy.

What is extinction, and under what conditions does it constantly occur?

The complete disappearance of a species from Earth; it is always occurring if organisms are not adapted or if environmental change is too rapid for adaptation.

Besides extinction, what two outcomes can changing environmental conditions lead to?

Increases in the number of individuals, and the emergence of a new species over time when groups evolve under different conditions.

What defines a mass extinction?

Rapid environmental changes on a global level that lead to $75\%$ or more of species going extinct.

What caused the K-Pg extinction, and which major organism groups went extinct?

It was caused by an asteroid impact, causing the extinction of dinosaurs, marine invertebrates, and land plants.

Which organism groups survived the K-Pg extinction?

Small mammals, birds, fungi, and ferns.

What specific characteristics allowed surviving organisms to endure the K-Pg extinction?

Being small (required less food), being burrowers (could hide), and being able to reproduce quickly (increased population size).

Why did mammals evolve and diversify after the extinction of dinosaurs?

There were fewer competitors and predators, more resources became available, and evolving plants provided new food sources and habitats.

What are phylogenetic trees?

Models that show evolutionary change and relationships between species.

How are common ancestors and closely related species arranged on a phylogenetic tree?

The common ancestor is in the tree trunk, organisms that evolved from it are at the ends of branches, and closely related organisms sit on branches close to one another.

What are fossils, and how do they support the concept of common ancestry?

Preserved remains or traces of ancient organisms found in sedimentary rock layers; their order provides a chronological timeline showing species changing and becoming more complex over time.

What are homologous structures?

Similar body parts shared by different animals, even if used for different functions, which suggest that the animals share a common ancestor.

What is an anatomical example of homologous structures given in the notes?

The front limbs of humans, bats, whales, and cats, which share the same bone structure (humerus, radius, ulna, carpals, metacarpals, phalanges) despite functions like writing, flying, or swimming.

What are vestigial structures, and what three examples are listed?

Structures that have lost their original function through evolution; examples include wisdom teeth, the tailbone, and the appendix.

How does comparative embryology provide evidence for common ancestry?

Embryos of different animals look very similar in early stages (for example, fish, bird, and human embryos all share gill slits and tails), suggesting inherited basic body plans from a common ancestor.

What does human DNA sharing about $98\%$ sequence similarity with chimpanzee DNA indicate?

It indicates that humans and chimpanzees share a recent common ancestor.

According to the Cytochrome c amino acid comparison data, which organisms had the fewest and most differences compared to humans?

The monkey had the fewest differences ($1$ difference), while mold had the most differences ($48$ differences).