1. 17-4 Patterns of Evolution

2. I. Extinction

3. Macroevolution - large-scale evolutionary patterns & processes that occur over long periods of time.

4. Six important topics in macroevolution are:
extinction
adaptive radiation
convergent evolution
coevolution
punctuated equilibrium
changes in developmental genes

5. Over 99% of all species that have ever lived are now extinct
Mass extinctions have:
provided ecological opportunities for organisms that survived
resulted in bursts of evolution that produced many new species

6. II. Adaptive radiation

7. Adaptive radiation - the process of a single species or a small group of species evolves into several different forms that live in different ways.

8. Adaptive Radiation of Mammals
Artiodactyls
Cetaceans
Perissodactyls
Tubulidentates
Hyracoids
Sirenians
Proboscideans
This diagram shows part of the adaptive radiation of mammals, emphasizing current hypotheses about how a group of ancestral mammals diversified over millions of years into several related living orders. Note that the dotted lines and question marks in this diagram indicate a combination of gaps in the fossil record and uncertainties about the timing of evolutionary branching.
Ancestral Mammals
Copyright Pearson Prentice Hall

9. The evolution mammals is an example of adaptive radiation b/c many species of mammals evolved from one ancestral species

10. III. Convergent evolution

11. Convergent Evolution- process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Ex: the similar nature of the flight/wings of insects, birds, pterosaurs (flying reptiles that are now extinct), and bats.

12. IV. coevolution

13. Ex: Predator/prey and parasite/host
Coevolution- A process that takes place with two species evolve in response to each other as time passes.
Ex: Predator/prey and parasite/host
Some Central American Acacia species have hollow thorns and pores at the bases of their leaves that secrete nectar (see image at right). These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores. berkeley.edu

14. v. Punctuated equlibrium

15. Gradualism- evolutionary change is slow and steady
Biologists have considered two different explanations for the rate of evolution, as illustrated in these diagrams. Gradualism involves a slow, steady change in a particular line of descent. Punctuated equilibrium involves stable periods interrupted by rapid changes involving many different lines of descent.
Copyright Pearson Prentice Hall

16. Punctuated equilibrium- a pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change.
Biologists have considered two different explanations for the rate of evolution, as illustrated in these diagrams. Gradualism involves a slow, steady change in a particular line of descent. Punctuated equilibrium involves stable periods interrupted by rapid changes involving many different lines of descent.
Copyright Pearson Prentice Hall

17. vi. Developmental genes & body plans

18. Scientist believe changes in genes for growth and differentiation during embryological development could produce changes in body shape and size.
Small changes in the activity of control genes can affect many other genes to produce large changes in adult animals.
Small changes in the timing of cell differentiation and gene expression can make the difference between long legs and short ones.
Copyright Pearson Prentice Hall

19. Evolution of Wings in Insects
Ancient Insect
Two Types of Modern Insects
Some ancient insects, such as the mayfly nymph (top), had winglike structures on many body segments. Modern insects have only four wings or two wings. Changes in the expression of developmental genes may explain how these differences evolved.
Copyright Pearson Prentice Hall