Chapter 4 Lecture Notes

Ecosystems: How They Change

Outline of Chapter 4

A. Population dynamics

B. Population equilibrium

C. Evolution

D. Succession

E. Living beyond our means

Dynamic Equilibrium

Ecosystems are constantly changing in order to stay balanced.

Succession - One species gradually replaced by another in an ecosystem

• primary – new ecosystem where there were no living things before. Cooled lava, receded glacier, mud slide

• secondary- ecosystem used to be there. Fire, humans clear an area

• Aquatic – (type of secondary) lakes taken over by terrestrial ecosystem

• Climax ecosystem- in balance only changes if major interference

Fires in Ecosystem

• Maintain balance of species and energy in ecosystems over the long run.

• Beneficial b/c provide nutrients for soil

• We avoid natural fires, but the problems like Crown Fires- (not natural) kill the whole tree

• 1988 Yellowstone fires changed climax ecosystems of white bark pine trees to huckle berries. Grizzlies ate both

Primary succession•Must create new soil for plants to grow•The first plants to come in are called pioneer species

The Basics of Evolutionary Change• Vocabulary

* DNA* Chromosome (46)* Gene –Coding region of the DNA* allele (23) – during meiosis, each egg or sperm receives one allele for each gene

• Central Dogma: DNA- blueprintRNA- carpenterProtein- house, pieces, wood

Each cell in an organism has the instructions.

Mutations

• Mutations are changes in DNA. They can occur by: * Normal variation* Chemical * UV * Radiation

• Genetic Trait- only passed down if an organism reproduces

• Good or Bad?

Why do species change?

• Selective pressure on DNA mutations from environmental resistance and biotic potential

• The time and space for evolution can be understood by knowing how old the earth is, how long life has been around, and Pangea.

Speciationexample

Reproductive Isolation

Understand how molecular biology (micro) relates to evolutionary change (macro) for

each of these vocabulary words:1. Adaptation2. Genetic variation3. Gene pool4. Differential reproduction5. Biological evolution6. Selective breeding7. Artificial selection8. Selective pressure9. Natural selection10. Fitness11. Evolution of a new species12. Reproductive isolation