1. Many ways for species to change….
Patterns of Evolution
Many ways for species to change….

2. Inherited traits that help organisms survive and reproduce
Adaptations
Inherited traits that help organisms survive and reproduce

3. Adaptations
Notice the spelling and pronunciation! “a-dap-tay-shuns” is correct (many people say “a-dap-shuns” – wrong!)
Adaptations = any inherited trait that helps an organism survive and reproduce (they’re nouns, not verbs!).
Adaptations can be physical (internal or external body parts), chemical (proteins, etc.), or behavioral (reflexes, instincts, or learning).

4. Adaptations, continued
Since adaptations are inherited, they can not change during an organism’s lifetime! Individuals can not adapt!! But species can adapt over many generations.
This seems confusing to us, since our major adaptation is our adaptability – but if an organism does not inherit a trait, it won’t suddenly develop it as needed. For example, a whale born without the gene to make blubber won’t be able to adapt – it will just die!

5. Examples of Adaptations
The fur of a polar bear
Insulin controlling blood sugar levels
An angler fish waiting for prey
A squirrel hibernating through the winter
Adrenaline signaling the body to speed up
The bright colors of a male peacock
The 4 chambers of mammal’s hearts
The ability to learn language
Structural
Chemical
Now tell if each of these is a structural, chemical, or behavioral adaptation!!
Behavioral
Behavioral
Chemical
Structural
Structural
Behavioral

6. Micro vs. Macroevolution
Microevolution occurs whenever a new trait becomes more common in a population (or when an old trait becomes less common) – but the population does not change enough to be considered a new species.
Macroevolution occurs whenever a population changes so much that they can no longer mate with other members of the original species. This results in new species, families, orders, or other large taxa (levels of classification).

7. Speciation I Speciation = The evolution of new species.
In order for a new species to evolve, it must stop reproducing with the original species. This is called reproductive isolation.
Repro isolation can happen in several ways:
Organisms can become separated in space, like getting stranded on an island, or separated by a mountain, a desert, or a river. This is called geographic isolation.
Organisms can become separated in time, with some nocturnal and other diurnal, or some mating in the spring and others in the fall. This is called temporal isolation.
Organisms can choose different kinds of mates, with some preferring one characteristic and others preferring another. This is called sexual selection.

8. Speciation II
Once the population has become reproductively isolated, it can evolve new traits or lose old traits depending on its environment and the process of natural selection.
These changes may also result from genetic drift, where random mutations lead to changes in the species.
Small populations that live at the edge of a species’ range are the most likely to change. This happens for two reasons:
A new gene can spread through a small population more easily, since the offspring with the new gene make up a larger percentage of the population.
The edge of a species’ range often has challenging environmental conditions that are difficult for organisms to survive in. This means that different genes are more likely to be useful than in the species’ main environment.

9. A Hypothetical Example of Speciation
Ground squirrels live in the deserts and the mountains. If the mountain squirrels hibernate until April, while the desert squirrels mate in February before it gets too hot, then the two populations will be reproductively isolated. The squirrels in the deserts could evolve traits to help them conserve water and to avoid overheating, while the squirrels in the mountains could evolve traits to help them survive the cold. Eventually, they become two different species.
A Hypothetical Example of Speciation

10. The Speed of Evolutionary Changes
Darwin thought that evolutionary changes were always very slow, taking up to 100,000 years. This is called gradualism.
Recently, scientists looked closely at the fossil record. Instead of finding constant slow changes in the fossils, they found that many species stayed the same for long periods of time, and then changed much more quickly than expected (maybe only taking 1000 years to change). This pattern is called punctuated equilibrium (a constant equilibrium punctuated by rapid changes).

11. More on Punctuated Equilibrium
The rapid changes could be caused by mutating a gene that acts on an embryo, making it very different from its parents. If the mutation is helpful, it could spread through the population and result in a new species.
Gradualism and punctuated equilibrium may seem like opposites, but they could both occur under different circumstances, with slow changes followed by a fast change, then a period of no change, then a fast change, a slow change, or any combination.

13. Divergent Evolution & Adaptive Radiation
Divergent Evolution occurs when a single species splits into two new species. The original species is the common ancestor of the new species, and although the two new species are still similar, they are too different to be able to reproduce. Each new species evolved new traits that fit its new environment or its new niche in the environment.
Adaptive Radiation occurs when divergent evolution happens repeatedly, resulting in several new species, all with the samecommon ancestor. Some of the new species may go extinct, while others may survive longer.

16. Adaptive Radiation of Hawaiian Honeycreepers

17. Convergent Evolution
Convergent Evolution occurs when unrelated species evolve similar characteristics. They look alike, but they do not become more closely related. They evolve similar traits because they are both living in a similar way in a similar environment (they have the same niche).
Convergent evolution results in analogous structures, while divergent evolution results in homologous structures.

19. Convergence of Marsupials and Placental Mammals

20. Parallel Evolution
Parallel Evolution occurs when two different species change in similar ways because their environment is changing. For example, we might predict that global warming would cause several unrelated species to evolve ways to survive hotter climates.

21. Coevolution
Coevolution occurs when two species influence each other’s evolution.
This could occur as an arms race, such as when the gazelle becomes faster to avoid the lion, so the lion becomes sneakier to catch the gazelle, then the gazelle gets better hearing, and the lion….
This could also result in symbiosis, like when an insect has the right shape to get nectar from a flower, so the flower drops pollen on it, and they become dependent on each other.

22. Types of Natural Selection
Natural Selection occurs in 3 ways, depending on how the environment influences the species. The traits change depending on whether the average trait or the extreme traits are favored.
Average Traits
are the most common
Extreme Traits
are the least common

23. Stabilizing Selection
If the environment is constant, and the average traits are favorable, the species becomes more alike over time. The extreme traits are lost since they are less helpful than the average traits. This is called Stabilizing Selection.
Result = 0 New Species

24. Directional Selection
If the environment changes, and one of the extreme traits is favored, the species changes into a new species. The extreme trait becomes more common since it is the most helpful in the new environment. This is called Directional Selection.
Result = 1 New Species

25. Diversifying Selection
If the environment favors both extreme traits, the species can split into 2 new species. Both extreme traits become more common since they are both helpful. This is called Diversifying Selection.
Result = 2 New Species