lecture 2 Flashcards Preview

ecology > lecture 2 > Flashcards

Flashcards in lecture 2 Deck (31)
Loading flashcards...
1

evolution

-mutations generally do not transform an organism that is already alive
-Mutations are inherited from parents to offspring.
-Evolution does not occur on an individual basis.
Evolution typically leads to alternate not ultimate forms
-Evolution requires a selection pressure in order to occur.

2

3 basics principles

individuals vs population
genetic diversity and heredity
selection (natural or sexual)

3

population

a group of individuals of one species living together
-populations are where evolutionary change is revealed

4

individual

is the reservoir of genetic information

5

Genetics

• All cells have DNA composed of 4 nucleotides arranged in an alpha helix – Each individual has a unique sequence of nucleotides in their DNA
• DNA is contained on threadlike structures called chromosomes
• Chromosomes come in matched pairs, one from each parent
• DNA is organized into discrete subunits called genes
– Locus - particular location of a gene on a chromosome
– BUT may have different versions (alleles) of that gene that code for
different versions of that trait.

6

populations are where evolutionary change occurs

• Alleles - two or more alternative forms of a gene
– result from slight differences in the DNA sequence of the gene
– cause slight differences in form and function

7

homozygote

an individual that has the same alleles at a particular locus on the pair
of chromosomes (AA, aa)

8

Heterozygote

an individual that has different alleles at a particular locus on the pair
of chromosomes (Aa)
– If one allele is fully expressed and the other has no noticeable effect
• Dominant allele – fully expressed (A) • Recessive allele – unexpressed (a)

9

mendelian inheritance

breeding of two individuals results in multiple
combinations of alleles
1 allele present on each chromosome of a parent
1 chromosome (allele) is present in each gamete produced by a parent
Gametes combine in offspring to form a new combination of alleles

10

genetics review

• Note: AA x AA = all AA and aa x aa = all aa
• 3 genotypes are produced: AA, aa, Aa
• genetic recombination - all possible allele combinations from random mating of
any combination of individuals in a population
• Mendelian Inheritance is how genetic variation is maintained

11

individual variation

genotype and phenotype

12

genotype

= all genetic characteristics of an individual
• morphological, physiological and behavioural • genetic characteristics are encoded in DNA
– Fixed during the lifetime of an individual

13

phenotype

= interaction of the genotype of an individual with its environment
• outward expression of genes in the appearance/behaviour of an individual
• Responses of individuals to environment may vary – Not Fixed during the lifetime of an individual
Individuals with the same genotype may look different under different environmental conditions

14

phenotypic plasticity

=the ability of a genotype to alter its phenotypic expression under different
environmental conditions

15

phenotypic variation can be expressed as

1. discrete
2. continuous

16

discrete

alternative forms
e.g. Social insects – such as bees and ants
two types of larvae hatch with essentially the same genetic material Queens - adults that reproduce
Soldiers/workers – adults that defend the other larvae

17

continuous

variations in form (continuously varying phenotypes)
– Reaction norm

18

reaction norm

relationship between response of a continuously varying trait
and environmental conditions

19

1 genotype can result in multiple...

phenotypes
e.g. Daphnia – respond (pigmentation) to varying UV radiation
• Avoid predators → transparent (no pigmentation)
• Avoid effects of harmful UV radiation → highly pigmented
- level of pigmentation varies continuously in response to UV radiation and predator abundance

20

There are limits to phenotypic plasticity!

(Responsiveness to environmental conditions)
-EX of a reaction norm: lower tolerance limit

21

evolutionary ecology underlying idea

– the match of individuals to their environment is a product of the successes and
failures of their ancestors
• the present form and function of individuals are specializations to their
environment
-alternate not ultimate forms

22

evolution

Evolution is a change in the genetic composition of a population of a species over time

23

adaptation

= the change in a genetically determined trait in response to environmental
conditions that enhances the ability to cope with the environment
evolutionary process that takes place in a population over many generations
through natural selection
• Traits can be behavioural, physiological or morphological

24

fitness

Fitness
= the proportionate contribution of an individual to future generations
• Number of offspring produced
• Number of offspring surviving to reproductive age

25

fitness is a ____ term

relative
– fittest individuals leave the greatest number of descendants relative to other
individuals

26

natural selection

• Operates on the individual
• Underlying concept:
– Individual variation has a genetic basis → traits are inherited – Individuals with favourable traits are more likely to reproduce
• these individuals leave more descendants than others
– Favourable traits are passed on to future generations at a higher frequency
Eg.
» Genetic composition of the population changes over generations or
evolves

27

what determines if a trait is favourable?

Selection pressures

28

selection pressures

• Environmental conditions - abiotic factors
• Species interactions (predators, competitors) – biotic factors
– selection pressures establish differences in fitness among
individuals with different genotypes and phenotypes

29

natural selection assumptions

1. Individuals of a species are not identical – genetic variation
2. Some of this variation is heritable
3. Individuals leave different numbers of descendants – varying fitness
4. Fitness depends on the interaction between an individual’s traits and its
abiotic & biotic environment

30

the environment acts as

selection pressures