Chapter 22 Descent with Modification: A Darwinian View of Life

________ refers to the process by which species accumulate differences from their ancestors as they adapt to different environments over time

• This definition is summarized by _________

Evolution

Darwin's phrase descent with modification

Greek philosopher _____ (384-322 BCE) believed that species were fixed (unchanging) • He arranged species on a scale of increasing complexity called the scala naturae • In the 1700s, scientists interpreted adaptations as evidence of design by a Creator

Aristotle

________ developed a nested classification system grouping similar species into increasingly inclusive categories • He also developed the binomial format for naming species (for example, humans are Homo sapiens) • Both of these systems are still in use today

Carolus Linnaeus (1707-1778)

• Darwin drew from the study of fossils, remains or traces of organisms from the past • Many fossils are found in sedimentary rock, which appears in layers called ____- • Stratigraphy • William Smith

strata

Paleontology, the study of fossils, was developed in large part by_______

Georges Cuvier (1769-1832)

_________ proposed that Earth's geologic features were formed gradually - For example, valleys being formed by rivers

James Hutton (1726-1797)

_______ proposed that the same geologic processes operate today as in the past, at the same rate • Uniformitarianism vs. Catastrophism • Darwin reasoned that the Earth must be older than the widely accepted age of a few thousand years • If true, gradual processes could also account for substantial biological change

Charles Lyell (1797-1875)

Jean-Baptiste de Lamarck (1744-1829) proposed two principles to explain evolutionary change

- Use and disuse: body parts used extensively become larger and stronger, unused parts deteriorate

- Inheritance of acquired characteristics: modifications acquired in one's lifetime can be passed to offspring

_____ are inherited characteristics that enhance an organism's survival and reproduction in specific environments

Adaptations

__________ is a process in which individuals with certain inherited traits tend to survive and reproduce at higher rates because of those traits

Natural selection

Descent with modification by natural selection explains three broad observations:

- The unity of life

- The diversity of life

- The ways organisms are suited to life in their environments

Humans modify species through _________, breeding only individuals with desired traits

artificial selection

Darwin drew two inferences from two observations

- Observation #1: Members of a population often vary in their inherited traits

- Observation #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce

Inference #1: Individuals with inherited traits that increase survival and reproduction in an environment tend to produce more offspring than other individuals

Inference #2: The unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Four types of data document the pattern of evolution

- Direct observations - Homology - The fossil record - Biogeography

__________are diagrams that reflect hypotheses about the relationships among groups • Homologies form nested patterns on the tree

Evolutionary trees

• Evolutionary trees show relative timing of events, not actual dates

___________ is determined by the recent common ancestor, not the proximity of groups on the tree

Relatedness

_____________is the evolution of similar, or analogous, features in distantly related groups • Analogous traits arise not through common ancestry, but through independent adaptation to similar environments

Convergent evolution

Evidence from biogeography, the scientific study of the geographic distribution of species, provides support for evolution • Species distributions are influenced by continental drift, the gradual movement of Earth's landmasses - For example, 250 million years ago, all landmasses formed a single large continent called Pangea - By 20 million years ago, they had drifted apart to form the continents near their present locations

_______________ occurs when heterozygotes have a higher fitness than both kinds of homozygotes

Heterozygote advantage

___________ will tend to maintain two or more alleles at that locus - For example, the deleterious sickle-cell allele is maintained at relatively high frequencies in some regions due to heterozygote advantage

Natural selection

Individuals with certain heritable traits survive and reproduce at a higher rate than other individuals • If the environment changes, natural selection may drive adaptation to new conditions, giving rise to new species

________increases the frequency of adaptations that are favorable in an environment

Natural selection