BIO 1220 - Lecture 9

what is adaptive radiation?

• the rapid production of many descendant species from a single lineage

• these descendant species have a wide range of adaptive forms

what are the three hallmarks of adaptive radiation

1. monophyletic group

2. speciated rapidly

3. diversified ecologically into many niches

what is a niche?

the range of resources a species can use and the range of conditions it can tolerate

what two factors trigger adaptive radiations?

• extrinsic factors - favorable new conditions in an environment

• intrinsic factors - evolution of traits

what is ecological opportunity?

• marked by availability of more or new types of resources

• driven a wide array of adaptive radiations

what is the cambrian explosion?

• the most spectacular evolutionary change in the history of life

• introduced more multicellular organisms

define fauna

a collection of animal species

what triggered the cambrian explosion?

1. higher oxygen levels:

• made aerobic respiration more efficient

2. rise of algae:

• enabled by increase in phosphorus, higher food quality

3. evolution of predation:

• exerted selection for shells and other defenses

4. new niches:

• move off ocean floor, diversification

5. new genes

• gene duplication and diversity increased hox genes

what are hox genes?

master controlling genes that guide the basic body plan

what is background extinction?

lower, average rate of extinction

what is mass extinctions?

extraordinary changes in the environment