1. Biology 13.3 Examples of Evolution

2. Biology 13.3 Examples of Evolution
Natural selection at Work:
The core of Darwin’s Theory of Evolution is that natural selection is the mechanism that drives evolution.
The key lesson that modern scientists have learned about natural selection is that the environment dictates the direction and amount of change.
Examples of adaptive camouflage

3. Biology 13.3 Examples of Evolution
Natural selection at Work:
If the environment changes in the future, than the characteristics that help an individual organism survive and reproduce successfully may change.
A polar bears white fur helps it blend in and hunt in it’s environment. In a different environment, this white fur would be a detriment rather than an advantage.
Examples of adaptive camouflage

4. Biology 13.3 Examples of Evolution
The process of natural selection is driven by 4 important factors:
All populations have genetic variation
The environment presents challenges to successful reproduction
Individuals tend to produce more offspring than the environment can support
Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring than those individuals less suited to the environment.
Examples of adaptive camouflage

5. Biology 13.3 Examples of Evolution
The process of natural selection is driven by 4 important factors:
1: All populations have genetic variation
In any population, there is an array of individuals that differ slightly from one another in genetic makeup.
While this is obvious in humans, it also is true in species whose members appear to us to be identical, such as bacteria that can cause common colds.

6. Biology 13.3 Examples of Evolution
The process of natural selection is driven by 4 important factors:
2: The environment presents challenges to successful reproduction.
Naturally, an organism that does not survive to reproduce or whose offspring die before the offspring can reproduce does not pass on it’s genes to future generations.

7. Biology 13.3 Examples of Evolution
The process of natural selection is driven by 4 important factors:
3: Individuals tend to produce more offspring than the environment can support.
Thus individuals of a population often compete with each other for food, shelter, and breeding partners.
Those best suited to attract a mate, have a better chance to breed and pass on genes.
Hundreds sea turtles hatch, few survive
Peacock’s plumage helps it attract mates

8. Biology 13.3 Examples of Evolution
The process of natural selection is driven by 4 important factors:
4: Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring.
Camels are an example of one animal that has developed over time to be able to survive in it’s harsh environment; being able to store large amounts of food and water to allow it to survive in the harsh environment of the deserts it inhabits.

9. Biology 13.3 Examples of Evolution
Examples of Evolution in bacteria:
Not all evolution takes place in obvious forms. Evolution also takes place, often rapidly, in bacteria such as common colds, flues or diseases.
In the 1950s, two effective antibiotics, isonaizid and rifampin, were used to treat tuberculosis.
In the 1980s. Two strains of tuberculosis appeared that were immune to these antibiotics.

10. Biology 13.3 Examples of Evolution
Examples of Evolution in bacteria:
How did these antibiotic strains of tuberculosis appear?
A mutation probably occurred within a single cell of tuberculosis within a patient who was ill. When treated with an antibiotic, the tuberculosis was wiped out in all the cells except the mutant cell.
The patient recovered temporarily but the one mutant cell still survived that was immune to the antibiotic.

11. Biology 13.3 Examples of Evolution
Examples of Evolution in bacteria:
This mutant cell was able to reproduce and again make the patient sick; this time killing the patient because the tuberculosis was now immune to any treatment.
In this way, the use of antibiotics to treat the illness led to the evolution of strains of the illness that were immune to the antibiotics.

12. Biology 13.3 Examples of Evolution
Examples of Evolution in bacteria:
This danger continues today and doctors worldwide have become much more careful in how readily they prescribe antibiotics out of fear of assisting the mutation of bacteria that cause a variety of diseases.

13. Biology 13.3 Examples of Evolution
Evolution of Darwin’s Finches:
Darwin collected 31 specimens of finches from three islands when he visited the Galapagos Islands.
In all, he collected 9 distinct species, all very similar to one another except for their bills.
Two ground finches with large bills feed on seeds that crush in their beaks, while two with narrower bills eat insects. One finch is a fruit eater, one picks insects out of cactus, while yet another creeps up on seabirds and uses it’s sharp beak to drink their blood.

14. Biology 13.3 Examples of Evolution
Evolution of Darwin’s Finches:
Darwin suggested the nine species if finches all developed from an original ancestral species.
Changes occurred as different populations adapted to different food sources.
In years when food was not as plentiful, those finches that had adaptations that aided them to get food in their immediate location survived and bred where their counterparts perished.

15. Biology 13.3 Examples of Evolution
Formation of new species:
The formation of species occurs in stages. Natural selection favors changes that increase reproductive success. Therefore, species molded by natural selection has an improved “fit” to it’s environment.
The accumulation of differences between groups is called divergence.
Divergence leads to the formation of new species.
Biologists call the process by which new species form speciation.

16. Biology 13.3 Examples of Evolution
Forming Subspecies:
Separate populations of a single species often live in several different kinds of environments.
In each environment, natural selection acts upon the population.
Natural selection results in offspring that are better suited to that environment.
If the environments differ enough, separate populations of the same species can become very dissimilar

17. Biology 13.3 Examples of Evolution
Forming Subspecies:
Over time, populations of the same species that differ genetically because of adaptations to different living conditions become what scientists call a subspecies.
The members of a newly formed subspecies have taken the first step toward speciation.
Eventually the subspecies become so different that they can no longer interbreed successfully.
Biologists than consider them a separate species.
Subspecies of rattlesnkaes
One of many species of snakes

18. Biology 13.3 Examples of Evolution
Maintaining new species:
What keeps new species separate? Why are even closely related species usually unable to interbreed?
Once subspecies become different enough, a barrier to reproduction usually prevents different groups from breeding with each other.

19. Biology 13.3 Examples of Evolution
Maintaining new species:
There are several types of barriers that may isolate two or more closely related groups.
Groups may be geographically isolated or may reproduce at different times.
Physical differences may also prevent mating, or they may not be attracted to one another for mating.
The hybrid offspring of a mating may not be fertile or may not be suited to the environment of either parent.

20. Biology 13.3 Examples of Evolution
Maintaining new species:
Scientists have seen the stages of speciation in many different organisms.
The ways that natural selection leads to the formation of new species has been thoroughly documented.
As changes continue to build over time, living species may become very different from their ancestors and from other species that evolved from the same recent common ancestor, leading to the formation of a new species.