Chapter 22: Descent with Modification

Evolution

Evolution

Descent with modification (phrase used by Darwin), or a change in genetic composition of a population from generation to generation

3 key observations about life

Organisms suited for their environments, the unity of life (shared characteristics), the diversity of life

Aristotle

A Greek philosopher, viewed species as fixed, made the scala naturae (or scale of nature, arranging species on a ladder), consistent with religious views

Carolus Linnaeus

Taxonomy, binomial format for naming species still used today (i.e. homo sapiens), classification for God

Fossils, strata, paleotology

The remains or traces of organisms from the past, layers of rocks, the study of fossils

Georges Cuvier

Largely developed paleontology, advocated for catastrophism, proposed that each layer of rock represented a catastrophe confined to a local area that wiped out a species, and then these areas were later repopulated by species immigrating from other areas

Catastrophism

The principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present

James Hutton

Gradualism (gradual change)

Charles Lyell

Uniformitarianism (mechanisms of change are constant over time)

Jean-Baptiste Lamarck

Published in 1809, the year Darwin was born; theory that as creatures use or don’t use certain body parts, they develop/grow according to this use and disuse, and then pass these new traits down (i.e. giraffes stretch their necks reaching for leaves and then pass this longer neck down); said evolution happened because creatures have an innate drive to become more complex

Charles Darwin — general information on his upbringing and journey

From England, his dad sent him to medical school but surgery freaked him out and medicine bored him, so he quit medical school and enrolled at Cambridge to become a clergyman. After he graduated, a professor at Cambridge recommended him to the captain of HMS Beagle. He was sort of just there for company and to keep the captain from losing his mind (he wasn’t even the ship’s naturalist). He experienced geologic change and witnessed differing species on mainlands and islands.

Adaptations

Inherited characteristics of organisms that enhance their survival and reproduction in specific environments

Natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates because of those traits

Why didn’t Darwin publish right away and what encouraged him to eventually?

He anticipated a great deal of backlash, and Alfred Russel Wallace shared the same theory with Darwin in 1858, so Darwin published in 1859 to get his out before Wallace’s

How many species that have ever lived are estimated to be extinct?

Over 99%

Artificial selection

Breeding individuals that possess desired traits

The 2 observations and 2 inferences

1. Members of a population vary in inherited traits 2. All species can produce more offspring than supported by their environment, and many fail to survive and reproduce 1. Better inherited traits tend to leave more offspring 2. Favorable traits accumulate in populations over generations

Thomas Malthus

Human suffering was a consequence of populations growing faster than food supplies and other resources

4 main pieces of evidence supporting evolution

Direct observations of evolutionary change, homology, the fossil record, and biogeography

Homology

Similarity resulting from common ancestry

Homologous structures

Structures that are anatomically similar but not necessarily similar in function due to a common ancestor (goes as far as genes)

Vestigial structures

Remnants of features that served a function in the organism’s ancestors (i.e. tailbones in humans)

Convergent evolution

The independent evolution of similar features in different lineages

Analogous structures

Similar in function, but no common ancestry (i.e. sugar gliders and flying squirrels)

Biogeography

The geogaphic distribution of species

Pangaea

The earth’s landmasses all united (has broken up, now we have continents)

Endemic

Found nowhere else in the world

Archbishop James Ussher

From Ireland, calculated the age of the earth (6,000 years)

Natural Theologians

19th century naturalists who “classified” the creation

Sexual selection

Building up traits that help them get a mate, not to survive (i.e. male birds have crazy feathers or dance moves to get women)

Punctuated Equilibrium

Pace of evolution is rapid, followed by periods of no change at all