Topic 6 Flashcards
Evolution
change in the genetic composition of a population of a species over time
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
Adaptation
change in a genetically determined trait in response to environmental conditions that enhances the ability to cope w the environment
Fitness
proportionate contribution of an individual to future generations
Fitness involves
- number of offspring produced
- number of offspring surviving to reproductive age
Natural selection operates on
the individual
Natural selection
differential success of individuals through interactions with their environment and other organisms
Variation results in
differences in growth, survival and reproduction
Fitness is measured by
the proportionate contribution an individual makes to future generations **
In a given environment traits which enable individuals to grow, survive and reproduce are passed on to future generations and.. and without those traits they are..
selected FOR; selected AGAINST
Selection pressures:
- environment conditions (abiotic factors)
- species interactions (biotic factors)
Selection pressures establish…
differences in fitness among individuals with different genotypes and phenotypes
Selected adaptations typical allow for optimal performance under a certain set of environmental conditions but these often..
limit its performance under another set
Genetic composition of the population..
changes over generations or evolves
Assumptions
- individuals of a species are not identical (genetic variation)
- some of this variation is heritable
- individuals leave different numbers of descendants (varying fitness)
- fitness depends on interaction between individual’s trait and its abiotic/biotic environment
Stabilizing selection
due to mendelian inheritance will maintain a diverse gene pool and evolution will not occur
Directional selection
most common type pushing traits in one direction to drive evolution
Disruptive selection
can lead to speciation
Directional selection as commercial fishing exploitation
atlantic silverside experiments in lab and coming fish at random is better for natural selection
Biological species concept
distinguish species based on their potential to interbreed and produce fertile offspring
Speciation
implies that reproductive isolation (or genetic isolation) defines a species because reproduction is the means of transferring genetic information (DNA)
Allopatric speciation
individuals are geographically isolated by a physical barrier (mountain). local environmental condition will cause different selective pressure leading to divergence
Sympatric speciation
subpopulations are isolated without geological isolation (breeding time, etc)
2 types of sympatric speciation
- pre mating
- post mating
Pre mating sympatric speciation
separation of mating events in space and time. behaviour (mating songs). mechanical or structural incompatibility
Post mating sympatric speciation
reduced survival or reproductive success of offspring
Cline
measurable, gradual, change over a geographic region in the average of some phenotypic character
Clines are typically associated with..
environmental gradients in temp, moisture, light levels, altitude (ex white tailed deer)
Ecotypes
population with an abrupt and dramatic difference in character due to influences associated within the species
Genetic differentiation
if very little gene flow exists between populations the term subspecies is often used.
Genetic differentiation is generally distinguished as..
different from other populations by 1 or more major characteristics (honey vs killer bee)
