The Pace of Speciation

1. The Pace ofSpeciation Section 25.3

2. Poll #1

3. Speciation- is the evolutionary process in which new species arise. • The pace of speciation refers to the rate of evolutionary change. • Scientists want to know this rate to further understand the concepts of evolution and natural selection. Background

4. Darwin suggested that evolutionary rates change over different periods of time. • Scientists who have been examining the patterns of speciation began to investigate two distinct patterns. • Neither of the two are considered completely flawless and are ways to classify the tempo of speciation. Background(cont.)

5. This theory suggests that new species evolve over long periods of time, but the evolution is constant and continuous. • This means that species are always evolving in small ways that may not be noticeable at first. • New species arise from many small changes that accumulated over a long period of time. Gradualism

6. This hypothesis on the pace of speciation theorizes that the tempo of change is much more irregular than phyletic gradualism suggests. • This belief states that there are periods of time where a species can have little to no phenotypic change. Punctuated equilibria • On the other hand, there are periods of time that the species will have rapid evolutionary change which leads to a new species. • During the time of little to no change, known as the equilibrium period. Neutral genetic changes are said to accumulate.

8. POLL #2

9. Factors that change the pace of Speciation • Allopatric speciation, which can also be termed as geographic isolation can effect the pace of speciation. • When a population of animals migrates away from a larger population a whole slew of new traits may arise relatively quickly. • If this population continues to develop new traits it may eventually become its own species.

10. Factors that change the pace of Speciation • Environmental shifts can also change the tempo of evolution. • When an environmental shift occurs that effects a species ability to survive it can drive speciation greatly. • The alleles that allow a species to survive the environmental shift will be very heavily favored therefore quickening the pace of evolution. A predator is an enviromental shift. Organisms that could hide from it have a better chance to survive.

11. Poll #3

12. Two theories are needed because both together most accurately explain speciation. • In many fossil records scientists observe species with long periods of time without any change, but than they have short periods of intense change. • Scientists hypothesize that the periods of little change are probably small neutral changes accumulating that were described in gradualism. DAFAQ #1“Why are two theories of speciation needed?”there are actually 3*

13. Yes, organisms have very different paces of speciation. • For example, bacteria are said to evolve much, much quicker than humans. This is because bacteria have many more generations than humans do. • Bacteria can reproduce a lot quicker, scientists say some can every 20 minutes. This is not even comparable to the speed that humans have to reproduce. • Therefore, bacteria have a much quicker pace of speciation. DAFAQ #2“Do different species have different timetables of speciation?”

14. This third hypothesis about the pace of speciation almost a hybrid of the previous theories. • The hypothesis is that a species is relatively stable in terms of evolution for a long period of time, but than undergoes a rapid change that does NOT lead to a new species. Punctuated Gradualism

15. The three hypotheses