1. Evolution and Speciation (Part 4)
Ms. Day
AP Biology
Chapter 24: The Origin of Life

2. How Does Evolution Work?
Populations produce more offspring than the environment can support
Carrying capacity sets the “limit”
The unequal ability of individuals to survive and reproduce (i.e.-an organism’s fitness) leads to the gradual change in a population over many generations
Allele frequencies (p and q) to change

3. RECALL: 3 Types of Natural Selection
Directional
Extreme form favored by natural selection
Stabilizing
Middle form most successful
Disruptive (Diversifying)
Two extreme forms successful in separate environments

5. Types of Evolution 1. Convergent evolution
organisms that are NOT closely related independently evolve similar traits as a result of having to adapt to similar environments.
Ex: Dolphins & fishes
Ex: Wings of bees & bats

6. 2. Divergent evolution 2 species gradually become different
Often occurs when closely related species diversify to new habitats
responsible for creation of current diversity of life on earth from the first living cells
Ex: Darwin’s finches
Type: Adaptive radiation

7. Hawaiian archipelago  Example of adaptive radiation
KAUAI
5.1
million
years
OAHU
3.7
HAWAII
0.4
1.3
MAUI
MOLOKAI
LANAI
Argyroxiphium sandwicense
Dubautia linearis
Dubautia scabra
Dubautia waialealae
Dubautia laxa N

8. 3. Coevolution 2 organisms evolve (change) in response to each other
Insects and the flowers (ex: orchids) they pollinate

9. 4. Parallel Evolution
2 species evolve independently of each other, maintaining similar traits
Usually occurs between unrelated species that do NOT occupy the same or similar habitats
Ex: Eutherians (placental) and Marsupial mammals

10. Review

11. Two Basic Patterns of Evolutionary Change
Anagenesis (phyletic evolution)
transforms one species into another
Cladogenesis (branching evolution)
the splitting of a gene pool, giving rise to one or more new species

12. LE 24-2
Anagenesis
Cladogenesis

13. How fast does evolution occur?
Gradualism
Species change slowly (gradually) over time
Punctuated Equilibrium
Species can make rapid “leaps” in evolution

14. Time
Gradualism model
Punctuated equilibrium model

15. What is a Species?
Species is a Latin word meaning “kind” or “appearance”
A population of organisms that produces viable fertile offspring in nature.
They can NOT interbreed with other populations

16. Similarity between different species  different behaviors and songs
Diversity within a species  defined by capacity to interbreed.

17. Speciation Speciation = the origin of new species
Must explain how new species originate and how populations evolve
Microevolution (genotype evolution)
adaptations that evolve within a population’s gene pool
Macroevolution (phenotype evolution)
refers to evolutionary change at the population level
Major biological changes evident in the fossil record