Unit 8 Evolution Notes Part 4: Patterns of Evolution & Evidence for Evolution

Patterns of Evolution 1.Divergent Evolution – Adaptive radiation 2.Convergent Evolution 3.Coevolution

Divergent Evolution 1.The process of two or more similar species becoming increasingly different 2.Species share a common ancestor that they split from 3.Species adapted differently to environment

Adaptive Radiation 1.Type of divergent evolution 2.One species or group evolved through natural selection into many diverse forms 3.Examples: – Darwin’s finches – Mammals after dinosaur extinctions

Adaptive Radiation

Convergent Evolution 1.Unrelated species come to resemble one another 2.Occurs because the organisms are adapted to similar environments 3.Example: Wings and flippers of aquatic birds, dolphins, and fish

Convergent Evolution Examples…

Coevolution A species evolves in response to another species Examples: Flowers and insects Flowers and hummingbirds Acacia tree and ants

Coevolution Video: Coevolution in Acacia & Ants Video: Coevolution in Acacia & Ants …

Evidence of Evolution How do we know evolution occurs? What evidence do we have in the natural world? How do we use this evidence?

Evidence of Evolution 1._________________________________ 2. _________________________________ 3. _________________________________ 4. _________________________________ Similarities in embryology Homologous body structures Geographic distribution of living things Fossil record

Fossil Record 1.Fossils are the remains of ancient organisms 2.Fossils show how species changed over time 3.Fossils show descent with modification and common ancestry

Fossil Record: How do we interpret fossil evidence? Stratigraphic Dating – Age of rocks based on geology – Younger rocks = closer to surface (usually)

Fossil Record: How do we interpret fossil evidence? Stratigraphic Dating – Age of rocks based on geology – Younger rocks = closer to surface (usually) Radiometric Dating – Based on radioactive decay (break down) of atoms – Carbon, uranium – Gives estimate of age

Geographic Distribution of Living Species Similarities in species that originated from a common ancestor. Similarities in species on different continents that live under similar ecological conditions. Think: How can two species that look very different from each other be more closely related than two other species that look a lot alike?

Geographic Distribution of Living Species

Homologous Body Structures 1.Homologous structures develop from the same embryonic tissue but grow into different forms 2.Show us descent with modification 3.Example: Limbs of animals with backbones (vertebrates)…

Homologous Body Structures of Vertebrates

Similarities in Embryology 1.In early stages of development, vertebrate embryos look VERY similar! 2.Embryo cells develop in similar orders and patterns 3.Homologous structures produced

Similarities in Embryology

Quick Quiz! 1.What is evolution? 2.What does “descent with modification” mean? 3.How does natural selection affect allele frequencies in a population? 4.What are the 4 forces of evolution? 5.What are the 4 main “categories” of evidence for evolution? 6.Approximately how old is the Earth?