Unit 1 Outline

Question 1

Darwin’s explanation of a certain trait in a certain animal

Answer 1

Natural Selection- organisms best suited to their environment survive and reproduce more successfully than other organisms. Thus, over time perhaps thousands to millions of years the proportion of organisms with tavorable traits increase in a species

1. Environment “screens out” (or SELECTS) features contributing to survival, and tends to eliminate others
2. Variations of inheritable features which already normally exist (organisms are all a little bit different)
3. Those with traits which help survival tend to survive and have more offspring, who inherit those traits.
4. New species, eventually

Question 2

Darwin’s theory of descent with modification

Answer 2

•States that newer forms appearing in the fossil records are actually the modified descendants of older species.
• Also stated that ALL living things descended from one, or a few common anscestors millions to billions of years agos
•This theory also accounted for the fact that similar organisms arise in the same geographical location (fig 15-6 pg. 281)

Question 3

Darwin’s theory of natural selection

Answer 3

• overproduction
• variation
• adaptation

Question 4

Overproduction

Answer 4

more organisms are born than can ultimately survive. There is competition within the species for food, habitat, survival from being eaten

Question 5

Variation

Answer 5

when organisms are born they are not all the same. There is variation (heritable differences that exist among individuals) that exists in every population (all the individuals of a species that live in an area and are capable of interbreeding) Natural-selection acts on existing variation and it acts on phenotypes (physical traits (observable)

Question 6

Adaptation

Answer 6

the “strong” or “best suited” that are selected by the environment (due to changes in climate, topography, food supply, predators etc) survive and pass these characteristics on to their offspring and these traits become more common in the population over time

Question 7

Best adapted species?

Answer 7

There are many diff environments and many diff demands on species. A species adapted to 1 environment might fare poorly in a diff environment. Diff types of orgaisms are interrelated in complex ways. Ex: animals depend on plants for their existence and plants depend on animals that feed on them for pollination.

Question 8

Speciation (HISTORICAL causes, geographic isolation)

Answer 8

Wegener suggested that the present continents had once been joined in a supercontinent he called Pangaea. He thought that these big land masses were floating apart over the Earth’s hot liquid interior. His theory is part of the theory of plate tectonics

Question 9

Types of speciation? (4)

Answer 9

Geographic isolation

Reproductive isolation

Temporal isolation

Behavioural isolation

Question 10

Geographic isolation

Answer 10

physical separation of members of a population. This could be caused by continental drift or a deep canyon for example. Once the subpopulations become isolated gene flow between them stops. Natural selection causes the two groups to become less alike. Eventually they are incompatible for mating.

Question 11

Reproductive isolation

Answer 11

results from barriers to successful breeding in groups in the same area. If the two extremes of a trait are selected for, the organisms may become so different that they are unable to mate. An example of this could be a toy poodle and a Newfoundland dog. The extreme sizes may cause the dog populations to become separate species.

Question 12

Temporal isolation

Answer 12

exists when timing prevents reproduction between populations. To reduce competition, courtship signs or reproductive periods may change.

Question 13

Behavioral isolation

Answer 13

isolation caused by different courtship or mating behaviors. Ex: firefly light flashing patterns are specific to each species. N p 325

Question 14

Generation time and evolution

Answer 14

Organisms with a short generation time (like prokaryotes) could be modified more rapidly than those with a long generation time. A bacterium with a gene ration time of 1 hour would have almost 9 million generations in 1,000 years - whereas humans would only have 40 generations in that same period. More generations= more variation= more chance of natural selection + eventually evolution?

Question 15

Obesogens - what are they and what concerns do doctors have about them?

Answer 15

Obesogens are an example of epigenetics. Obesogens are compounds which cause weight gain
- They directly affect adipocytes (fat cells)
- They change metabolism
- It changes the way the body regulates hunger