Ch. 22 Warm-Up Compare and contrast natural selection vs. artificial selection. What are the key ideas of natural selection? Define and give an example for the following: Homologous structure Vestigial structure Analogous structure

Descent with Modification Part B: Evidence for Evolution Chapter 22 Descent with Modification Part B: Evidence for Evolution

Recap main ideas of natural selection: Evolution is change in species over time. There is overproduction of offspring, which leads to competition for resources. Heritable variations exist within a population. These variations can result in differential reproductive success. Over generations, this can result in changes in the genetic composition of the population. Remember: Individuals do NOT evolve! Populations evolve.

Evidence for Evolution: Direct Observations Homology Fossil Record Biogeography

Evidence for Evolution 1. Direct Observations 2. Homology 3. Fossil Record 4. Biogeography

Evidence for Evolution: 1. Direct Observations Examples: Soapberry bugs( beak length) Insect populations become resistant to pesticides (DDT) Antibiotic-resistant bacteria (MRSA) Peppered moth (pollution in city vs. country)

The Rise of MRSA (methicillin-resistant Staphylococcus aureus)

Evidence for Evolution: 2. Homology Homology: characteristics in related species can have underlying similarity even though functions may differ Examples: Homologous structures: similar anatomy from common ancestors (eg. forelimbs of human/cat/whale/bat) Embryonic homologies: similar early development not visible to adults (eg. vertebrate embryos with tail & pharyngeal pouches) Vestigial organs: structures w/little or no use (eg. flightless bird wings) Molecular homologies: similar DNA and amino acid sequences

Homologous Structures

Embryonic Development

Vestigial Structures

Molecular Homologies Compare DNA and amino acid sequences

Convergent Evolution Distantly related species can resemble one another. Do not share a common ancestor. Analogous structures: various structures, function in similar environments Eg. Torpedo shape of shark, penguin, & dolphin In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. Suger glider is a marsupial and flying squirrel is eutherian.

Evidence for Evolution: 3. Fossil Record Fossils = remains or traces of organisms from past Found in sedimentary rock Paleontology: study of fossils Show evolutionary changes that occur over time and origin of major new groups of organisms Cetaceans ( aquatic mammals) Ungulates( large mammals including odd-toed ( horse) and even toed ( pig, giraffe, camels) Ankle bones

The fossil record shows that over time, descent with modification prtoduced increasingly large differences among related groups of organisms.

Evolutionary Tree Based on anatomical and DNA sequence data

How to interpret data from a evolutionary tree? 1- How many ancestors can you recognize in the above evolutionary tree? List them from the oldest to the most recent one. 2-Why are scientists feel confident that the above evolutionary tree accurately reflects the evolutionary history? 3- How many traits being studied to create the above tree by scientists? 3-Are mammals closer to amphibians or birds? Explain from the tree. 4- Are ostriches closer to crocodiles or birds? Explain from the tree. 5-How are mammals and birds both related to amphibians?

Evidence for Evolution: 4. Biogeography Biogeography = geographic distribution of a species Species in nearby geographic areas resemble each other Continental drift and Pangaea explains similarities on different continents Endemic species: found at a certain geographic location and nowhere else Eg. Marine iguanas in the Galapagos

Island Biogeography

Tree of Life

Check for understanding