Chapter 15: Evolution…What is it



Chapter 15: Evolution…What is it? Name: ____________________________

Fossils shape ideas about evolution:

1. When evidence indicated that Earth was much older than many people had thought, biologists

began to suspect that species change over time, or _______________.

2. _________________ are an important source of evolutionary evidence because they provide a record of early life and evolutionary history.

3. Simple definition = _____________________________________

1831: Enter Charles Darwin

Son of wealthy parents; Lead a privileged life; Dropped out of medical school; Enjoyed walking in nature & collecting beetles

The Voyage that Changed the World

4. ____________________ sailed around the world on a ____ year voyage. At the age of _____,

Darwin soon became the ship’s naturalist.

What Darwin Observed on the Voyage

5. ______________ animals were similar to animals today.

6. Fossil seashells found high in mountains.

7. ____________________ can lift the land several feet at a time.

8. Life is _______________ to specific habitats.

9. There is much _________________ in populations within each generation.

Darwin’s “Theory” of Evolution has many components

10. _____________________, _______________________, __________________________

Malthus’ Contentions

11. English economist Thomas _______________ had proposed an idea that Darwin modified and

used in his explanation.

12. Malthus’s idea was that the __________________________________________________ and

nature would intervene through starvation, disease and war.

Darwin’s Insight…Natural Selection

13. Animal populations grow faster than food supplies…

14. Members of each generation must ________________ for limited resources…

15. ______________________ members have traits that gave them an advantage in competition…

16. ___________________________ those traits that are successful under the present conditions.

Darwin continues his studies

Darwin observed that the traits of individuals vary in populations. Variations are then inherited.

17. Breeding organisms with specific traits in order to produce offspring with identical traits is

called _____________________________________.

Darwin hypothesized that there was a force in nature that worked like artificial selection.

18. __________________________________ is a mechanism for change in populations.

“Darwinism”

19. Species are not fixed but rather change _________________over time.

20. Natural selection works on the _________________________________ in each population.

21. As differences build up over time _________________________ arise. Therefore, different

species have common ancestors in time.

Adaptations: Evidence for Evolution

22. ____________ = Any variation that aids an organism’s chances of survival in its environment.

Adaptation: Mimicry

23. ________________ is a structural adaptation that enables one species to resemble another species. A harmless species has adaptations that result in a physical resemblance to a harmful species. Predators that avoid the harmful looking species also avoid the similar-looking harmless species. Also, two or more harmful species can resemble each other.

Adaptation: Camouflage

24. __________________ = An adaptation that enables species to blend with their surroundings.

Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

Physiological Adaptations

25. ___________________________________ are changes in an organism’s metabolic processes.

In addition to species of bacteria, scientists have observed these adaptations in species of insects and weeds that are pests.

Anatomy: Evidence for Evolution

26. Structural features with a common evolutionary origin are called

_____________________________________.

27. Homologous structures can be ___________________________________________________.

28. The body parts of organisms that do not have a common evolutionary origin but are similar in ________________ are called _______________________________________________.

For example, insect and bird wings probably evolved separately when their different ancestors adapted independently to similar ways of life.

29. A _____________________________________ is a body structure in a present-day organism

that no longer serves its original purpose, but was probably useful to an ancestor.

Embryology: Evidence for Evolution

30. An embryo is the earliest stage of growth and development of both plants and animals.

The embryos of a fish, a reptile, a bird, and a mammal have a tail and pharyngeal pouches.

Biochemistry: Evidence for Evolution

31. Nearly all organisms share ________________________________________________ among

their biochemical molecules.

Organisms that are biochemically similar have fewer differences in their amino acid sequences.

Today, scientists combine data from fossils, comparative anatomy, embryology, and biochemistry in order to interpret the evolutionary relationships among species.

Populations, not individuals, evolve

Evolution occurs as a population’s genes and their frequencies change over time.

32. Picture all of the alleles of the population’s genes as being together in a large pool called a

___________________.

33. The percentage of any specific allele in the gene pool is called the

_______________________________________.

34. They refer to a population in which the frequency of alleles remains the same over generations

as being in ____________________________________________.

Changes in Genetic Equilibrium

35. A population that is in genetic equilibrium is _________________________.

36. Any factor that affects the genes in the gene pool can change __________________________,

disrupting a population’s genetic equilibrium, which results in the process of evolution.

37. One mechanism for genetic change is _______________. Environmental factors, such as

radiation or chemicals, cause many mutations, but other mutations occur by chance.

38. Another mechanism that disrupts a population’s genetic equilibrium is

________________________—the alteration of allelic frequencies by chance events.

Genetic equilibrium is also disrupted by the movement of individuals in and out of a population.

39. The transport of genes by migrating individuals is called ____________________.

3 Types of Natural Selection

40. ______________________, ________________________, _________________________

41. Draw 3 curves

The Evolution of Species

42. The evolution of new species, a process called ___________________ occurs when members

of similar populations no longer interbreed to produce fertile offspring within their natural

environment.

In nature, physical barriers can break large populations into smaller ones.

43. ______________________________ occurs whenever a physical barrier divides a population.

Reproductive Isolation can result in Speciation

44. ________________________________________ occurs when formerly interbreeding

organisms can no longer mate and produce fertile offspring.

45. The ___________________ material of the populations can become so different that

fertilization cannot occur. Another type of reproductive isolation is __________________.

Speciation Rates

46. _________________ is the idea that species originate through a gradual change of adaptations.

47. In 1972, Niles Eldredge and Stephen J. Gould proposed a different hypothesis known as

____________________________________________.

This hypothesis argues that speciation occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium in between.

Diversity in New Environments

48. When an ancestral species evolves into an array of species to fit a number of diverse habitats,

the result is called _____________________________________.

49. Adaptive radiation is a type of ______________________________________, in which

species that were once similar to an ancestral species become increasingly different.

50. A pattern of evolution in which distantly related organisms evolve similar traits is called

____________________________________.

This occurs when unrelated species occupy similar environments in different parts of the world.

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