Evolution. In the 18 th century, people became more mobile. Lamarck. Organisms acquire characteristics and pass them on WRONG!!!

Transcription

1 Evolution In the 18 th century, people became more mobile Why are the different animals and plants in different geographic areas? How do we explain this diversity? As fossils were discovered: why don t these organisms exist anymore and why do the things living today look totally different from these fossils? Until mid 19 th century: Each species was individually created and has remained unchanged over time Lamarck proposed: Each species is a unique individual creation but changes over time Organisms acquire characteristics and pass them on WRONG!!! Lamarck (c) Descent with modification Darwin and Wallace: Species descend from a common ancestor 1

2 Lyell Influences on Charles Darwin - Earth is older than previously thought - Small changes over time have produced the geology that we see today Malthus. - Populations grow resources limit growth. Darwin and the theory of evolution Descent with modification leads to evolution of new species The process of natural selection explains how The Voyage of HMS Beagle Credit. Dr. R. Rothman Figure 22.7 Descent with modification The Hawaiian Silversword Alliance 2

3 Darwin s observations of natural populations: Evolution: How Does Evolution Really Work? Overproduction of offspring. Variation within populations exists and is inherited from the parents Struggle for resources and thus survival. Differential survival and reproduction. Individuals have different fitness. Fitness is the ability to survive and reproduce offspring Natural Selection - Adaptation Artificial Selection Adaptations Source: Evolution = process of change over time How do fossils form? Evidence comes from a variety of sources 1) fossils 2) biogeography 3) anatomical similarities - Homology - Convergent evolution 5) Molecular data 3

4 Figure Figure 25.1 A gallery of fossils Homology and Convergent Evolution Biogeography Biogeography is the study of the geographic distribution of organisms Organisms of the Galapagos are more similar to those of mainland South America rather than other tropical islands. Related species are found in distant geographic areas. Figure 25.4 The history of continental drift Continental Drift explains some species distributions Key: C = Cassowary; E = Emu; e = Elephant Bird; K = Kiwi; m = Moa; O = Ostrich; R = Rhea. 4

5 Molecular Evidence Microevolution and Macroevolution Microevolution changes within species Macroevolution how species evolve How does Microevolution happen? Mutations: Chromosomal Changes It occurs at the population level Mutations Migration Genetic Drift Deletion Translocation Inversion Insertions Migration Genetic drift The frequency of alleles increases or decreases due to random chance (can also be due to selective forces like habitat loss or mass overhunting) Grass in the foreground is growing on mine tailings The same species is growing in the background 5

6 Bottleneck Effect Macroevolution is due to isolation Reproductive Isolation Geographic isolation Ecological isolation Reproductive Isolation Geographic Isolation Eastern redbud east of Mississippi Western Redbud California, Utah, Nevada and Arizone Ecological Isolation Macroevolution factors such as climate or soils may play a role in isolation Dutchman Breeches Squirrel Corn Role of Hybridization in Evolution Hybrids may be significant or important in evolutionary change, depending on how the characteristics of the parents were combined. Introgression - Backcrossing between hybrid and parent. Polyploidy - New cell wall fails to develop between two daughter cells. Sterility - Chromosomes do not pair up correctly. 6

7 Apomixis Sterile Hybrids may reproduce asexually. Apomixis includes the development and production of seeds without fertilization. - May be highly successful. Dandelions and Wild Blackberries Copyright McGraw-Hill Companies Permission Required for Reproduction or Display Copyright McGraw-Hill Companies Permission Required for Reproduction or Display Figure