lecture 2 Flashcards
(31 cards)
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.
3 basics principles
individuals vs population
genetic diversity and heredity
selection (natural or sexual)
population
a group of individuals of one species living together
-populations are where evolutionary change is revealed
individual
is the reservoir of genetic information
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.
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
homozygote
an individual that has the same alleles at a particular locus on the pair of chromosomes (AA, aa)
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)
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
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
individual variation
genotype and phenotype
genotype
= all genetic characteristics of an individual
• morphological, physiological and behavioural • genetic characteristics are encoded in DNA
– Fixed during the lifetime of an individual
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
phenotypic plasticity
=the ability of a genotype to alter its phenotypic expression under different
environmental conditions
phenotypic variation can be expressed as
- discrete
2. continuous
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
continuous
variations in form (continuously varying phenotypes)
– Reaction norm
reaction norm
relationship between response of a continuously varying trait
and environmental conditions
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
There are limits to phenotypic plasticity!
(Responsiveness to environmental conditions)
-EX of a reaction norm: lower tolerance limit
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
evolution
Evolution is a change in the genetic composition of a population of a species over time
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
fitness
Fitness
= the proportionate contribution of an individual to future generations
• Number of offspring produced
• Number of offspring surviving to reproductive age
