Chapter 4 Evolution, Biological Communities, and Species Interactions

1. Chapter 4 Evolution, BiologicalCommunities, and Species Interactions

2. “Of course, long before you mature, most of you will be eaten.”

3. “The picture’s pretty bleak, gentlemen. The earth’s climate is changing, the mammals are taking over, and we all have brains the size of a walnut.”

4. “Now this end is called the thagomizer, after the late Thag Simmons.”

5. “Evolution’s been good to you, Sid.”

6. Evolution Produces Species Diversity • Natural Selection Leads to Evolution • All Species Live Within Limits • The Ecological Niche is a Species’ Role and Environment • Large Grassland Herbivore • North America: Pronghorn • Africa: Antelope • Australia: Large Kangaroos • Speciation Maintains Species Diversity

7. Exaptation

8. There Are No Half-Evolved Organisms • Every organism is adapted to its environment all the time • Change happens when the environment changes • Mass Extinctions • Exotic Species Invasions • Climate Change

9. What Good is Half an Eye?

10. What Does a Bug See?

11. What Does a Bug See?

12. What Good is Half a Wing? • It’s about Terminal Velocity • Humans: 50m/sec (Really terminal) • Mice: 5 m/sec (Generally not terminal) • True Powered Flight • Birds • Bats • Insects • Flying Reptiles (Maybe)

13. What Good is Half a Wing? • Critters that Glide • Squirrels • Marsupials • Lemurs • Fish • Squid • Lizards • Snakes • Frogs

14. What Good is Half a Wing? • Critters that Glide are all Small • Low Terminal Velocity • Falls usually not fatal • Selection favors duration and control • Pre-Flight Uses for Wings • Catching prey • Mating displays • Fighting • Ground maneuverability

15. The Bumblebee Myth • Bumblebees, theoretically, can’t fly • They can’t glide. Neither can an F-16 • Bumblebees can carry more than their own weight, something no aircraft can do • C-130 transport: empty weight of 76,780 pounds and a maximum takeoff weight of 175,000 pounds • A C-5 Galaxy: empty weight of 238,000 pounds and a maximum takeoff weight in wartime of 840,000 pounds

16. Species Interactions Shape Biological Communities • Competition Leads to Resource Allocation • Predation Affects Species Relationships • Some adaptations help avoid predation • Symbiosis involves intimate relations among species • Keystone species have disproportionate influence

17. Community Properties Affect Species And Populations • Productivity is a measure of biological activity • Abundance and diversity measure the number and variety of organisms • Cormnunity structure describes spatial distribution of organisms • Complexity and connectedness are important ecological indicators • Resilience and stability make communities resistant to disturbance • Edges and boundaries are the interfaces between adjacent communities

18. Communities Are Dynamic And Change Over Time • The nature of communities is debated • Ecological succession describes a history of community development • Appropriate disturbances can benefit communities • Introduced species can cause profound community change