Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 22 Descent with Modification: A Darwinian View of Life

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Darwin’s Focus on Adaptation In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes From studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to the Galápagos finches

Fig (a) Cactus-eater(c) Seed-eater (b) Insect-eater

Fig. 22-6a (a) Cactus-eater

Fig. 22-6b (b) Insect-eater

Fig. 22-6c (c) Seed-eater

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Origin of Species Darwin developed two main ideas: – Descent with modification explains life’s unity and diversity – Natural selection is a cause of adaptive evolution

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Descent with Modification The phrase refers to the view that all organisms are related through descent from a common ancestor that lived in the remote past

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings In the Darwinian view, the history of life is like a tree with branches representing life’s diversity

Fig Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) Millions of years ago Years ago Platybelodon

Fig. 22-8a Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) Millions of years ago Years ago Platybelodon

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Artificial Selection, Natural Selection, and Adaptation Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection Darwin then described four observations of nature and from these drew two inferences

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings What’s the difference between natural selection and artificial selection?

Fig Kale Kohlrabi Brussels sprouts Leaves Stem Wild mustard Flowers and stems Broccoli Cauliflower Flower clusters Cabbage Terminal bud Lateral buds

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Observation #1: Members of a population often vary greatly in their traits

Fig

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support

Fig Spore cloud

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings If some heritable traits are advantageous, these will accumulate in the population, and this will increase the frequency of individuals with these adaptations This process explains the match between organisms and their environment

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Natural Selection: A Summary Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals Natural selection increases the adaptation of organisms to their environment over time If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species Video: Seahorse Camouflage Video: Seahorse Camouflage

Fig a (a) A flower mantid in Malaysia

Fig b (b) A stick mantid in Africa

Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Note that individuals do not evolve; populations evolve over time Natural selection can only increase or decrease heritable traits in a population Adaptations vary with different environments