Evolution: History and Evidence Chapter 4 Evolution: History and Evidence

Evolution: History and Evidence Organic Evolution Darwin “Descent with modification” Populations change over time.

Pre-Darwinian Theories of Change Greek philosophers Empedocles (495-435 B.C.) Aristotle (384-322 B.C.) Buffon (1707-1788) Erasmus Darwin(1731-1802) Lamarck (1744-1829) Change results from “need”

Voyage of HMS Beagle Charles Darwin (1809-1882) Boarding school Edinburgh medical school Christ’s College Cambridge Nominated by Henslow to serve as naturalist on HMS Beagle (1831) On Origin of Species by Means of Natural Selection (1859)

Figure 4.1 Voyage of the HMS Beagle.

Early Development of Darwin’s Ideas of Evolution Geology Hutton and uniformitarianism Geological change occurs over hundreds of millions of years. Earth is much older than 6,000 years. Could not living forms change as well?

Early Development of Darwin’s Ideas of Evolution Fossil evidence South American fossils Figure 4.2a The giant sloth.

Early Development of Darwin’s Ideas of Evolution Galapagos Islands Tortoises Finches Adaptive radiation The formation of new forms from an ancestral species Figure 4.3a Galapagos tortoise (Geochelone elephantopus).

Figure 4.4 Adaptive radiation of Galapagos finches.

The Theory of Evolution by Natural Selection Other observations Artificial selection Thomas Malthus (1766-1834) (b) (a) Figure 4.5 Artificial selection in Canis lupis. The 147 breeds of dogs recognized by the AKC originated from artificial selection of wolf ancestors. The grey wolf (a), Shetland Sheep Dog (b), and Irish Wolfhound (c). (c)

The Theory of Evolution by Natural Selection High reproductive potential Inherited variation exists. Constant struggle for limited resources, many individuals die. Adaptive traits become more common in subsequent generations.

Adaptation Occurs when a HERITABLE CHANGE IN PHENOTYPE increases an animal’s chances of SUCCESSFUL REPRODUCTION Examples? Arise as a result of chance mutations Perpetuated by natural selection Figure 4.6 Adaptations of the Arctic Hare (Lepus articus).

Alfred Russel Wallace (1823-1913) Theory of evolution similar to Darwin’s Published ideas jointly with Darwin Impetus for Darwin’s publication of On the Origin of Species by Means of Natural Selection Darwin given credit Years of work Massive accumulations of evidence

Microevolution, Macroevolution, and Evidence of Macroevolutionary Change Change in the frequency of alleles in a population over time Macroevolution Large-scale changes that result in the extinction and formation of new species

Biogeography Study of the geographic distribution of plants and animals Life-forms in different parts of the world have distinctive evolutionary histories. Biogeographers attempt to explain distribution patterns.

Figure 4.7 Biogeography as evidence of evolutionary change.

Figure 4.8 Biogeographic regions of the world.

Paleontology Fossils Evidence of plants and animals that existed in the past and have become incorporated into the earth’s crust Direct evidence of sequences of appearance and disappearance of organisms

Paleontology Figure 4.10 The fossil record gives evidence of the horse lineage. Figure 4.9 Fossils like this trilobite are direct evidence of evolutionary change.

Analogy and Homology Convergent evolution Homology Evolution of superficially similar structures in unrelated organisms Similar structures are analogous. Homology Resemblance that occurs because of common ancestry

Homology—Comparative Anatomy Study of the structure of living and fossilized animals and homologies that indicate close relationships Figure 4.11 Vertebrate forelimbs evolved from an ancestral pattern.

Figure 4.12 Evolution of the vertebrate ear ossicles.

Figure 4.13 Vestigial structures have no apparent function in an animal, but evolved from functioning structures in ancestors.

Homology—Developmental Patterns Developmental stages of related animals often retain common features. Changes in genes controlling development are usually harmful and eliminated by natural selection. Figure 4.14 Early developmental stages of vertebrates are similar.

Homology—Molecular Biology Study of nuclear DNA, mitochondrial DNA, ribosomal RNA, and proteins Molecules provide direct evidence of change in genes. Genetic similarity (degree of relatedness) is reflected in variation in amino acid sequences in proteins and base sequences in DNA.

Interpreting the Evidence: Phylogeny and Common Descent Evolutionary relationships among species

Phylogenetic Trees Show lines of descent Branches Nodes Evolutionary connections Nodes Branch points Genes, populations, or species where a change occurs

Modern Synthesis Principles of modern genetics combined with Darwinian evolutionary theory Chapter 5