Chapter 11.4 Flashcards Preview

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Flashcards in Chapter 11.4 Deck (12)
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1
Q

The most important mechanism of evolution

A

NATURAL SELECTION

2
Q

How does Natural selection change the genetic makeup of a population

A

by favoring the alleles that contribute to the reproductive success and selecting against those that are harmful

3
Q

Natural selection does not eliminate alleles directly, Instead….

A

Individuals with the best phenotypes are more likely to survive long enough to reproduce, those with poorly suited phenotypes are are less likely to survive to reproduce

4
Q

What are the 3 modes of Natural Selection

are distinguished by their effects on the phenotypes ina population

A
  1. Directional selection

2. Disruptive selection

3. Stabilizing

5
Q

How are the 3 modes of natural selection distinguished

A

by their effects on the phenotypes in a population

6
Q

DIRECTIONAL SELECTION

A

one extreme phenotype is the fittest and the environment selects against the others

eg. dark tree trunk with white wing moths

mrsa

7
Q

DISRUPTIVE SELECTION

A

( DIVERSIFYING SELECTION)

2 or more extreme phenotypes are fitter than the intermediate phenotype

8
Q

STABILIZING SELECTION

A

( NORMALIZING SELECTION)

Extreme phenotypes are less fit than the intermidiate

It tends to reduce variation in apopulation and is therefore more common in stable unchanging environment

9
Q

BALANCED POLYMORPHISM

A

multiple alleles of a gene persists indefinately in the population at more or less constant frequencies. ( even harmful ones)

10
Q

Circumstances where natural selection maintains BALANCED POLYMORPHISM

A

Heterozygous advantage

11
Q

HETEROZYGOUS ADVANTAGE

A

A circumstance of balanced polymorphism when an individual with 2 different alleles for a gene ( heterozygote) has geater fitness than those whose alleles are identical.

Heterozygotes maintain harmful recessive allele in apopulation evenif homozygous recessive individuals have greatly reduced fitness

Heterozygotes with disease have a reproductive edge than homozygotes (why natural selection does not remove an harmful allele in heterozygotes)

12
Q
A