Unit 4, topic 2 Flashcards
define evolution
Evolution - change in the genetic composition of a population during successive generations, which may result in the development of new species.
define microevolution and give an example
Microevolution - small-scale variation of allele frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor. - the outcome of natural selection.
EG: acquisition of antibiotic resistance in a population of bacteria, after antibiotic exposure.
define macroevolution and give an example
Macroevolution - the variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor.
A single species with adaptation that allow it to exploit new ecological roles eventually gives rise to a new group of organisms comprising new species.
EG: formation of species from a single ancestral dinosaur following a mass extinction event.
what did lamarck propose
Lamarck
Suggested that organisms pass on their findings to their offspring characteristics that they acquire during their lifetimes and proposed that individual efforts during the lifetimes of organisms were the mechanism that drives adaption.
what did darwin and wallace propose
Wallace and Darwin
Darwin referred to their theory as descent with modification – that life today has descended from common ancestors that were generally different from their modern descendants.
Natural selection – the process in which individuals with certain inheritable characteristics traits that are most advantageous to their environment and hence survive and reproduce more successfully than other individuals leading to evolutionary change in the population.
define continental drift
Continental drift – the relative movement of Earth’s continental landmasses that appear to drift or float over the Earth’s mantle.
Pangea – supercontinent
what have been the changes in climate and on earth
Changes in climate
Earth was much warmer than it is today and the temperature difference between the equator and the poles was not as large. Sea levels were lower, ice sheets covered much of the earth’s surface.
Changes in life on Earth
Evolutionary radiation - refers to an increase in taxonomic diversity or morphological disparity.
Follows mass extinctions because it major competitors are removed, and survivors have unprecedented access to new habitats and no longer had to compete for resources.
describe gene pools
Gene pools
The range of genes and all their alleles present in a population
Genetic mutations introduce new alleles into populations. It is this variation in alleles carried by different individuals that leads to most of the variation in a population.
The range of variation possible in a gene pool is restricted by the alleles available.
EG: bearded dragons do not carry genes for wings but they do carry genes for 4 legs, tail, and scales – the many genes that only have one possible allele. Therefore they do not contribute to any variation and are said to be’fixed.’
describe allele frequencies
Allele frequencies
For variation to occur in phenotypes more than one allele must exist. Phenotypes that vary due to genetic differences are termed ‘genetic polymorphisms.’ The frequency of polymorphism alleles can be affected by:
Mutation of an allele
Immigrations of individuals
Emigration of individuals
The reproduction rate of various individuals in the population.
what can allele frequency be affected by
Allele frequencies
For variation to occur in phenotypes more than one allele must exist. Phenotypes that vary due to genetic differences are termed ‘genetic polymorphisms.’ The frequency of polymorphism alleles can be affected by:
Mutation of an allele
Immigrations of individuals
Emigration of individuals
The reproduction rate of various individuals in the population.
describe genetic drift
Genetic drift
Random changes in a small populations due to a chance event.
EG: there is a chance that some alleles present in a parental group will not be passed onto the offspring at all - which means they may be permanently lost from the gene pool (in small populations).
Can give rise to the bottle neck effect or when a small group migrates and establishes a population in a new location – the founder effect may occur.
describe the bottle neck effect
Bottle neck affect
Certain alleles may be lost through chance due to a catastrophic event or period of adverse changes that drastically reduced the size of a pop.
If some of the pop is recovered, the original pop gene pool cannot be recovered.
EG: facing a declined population, surviving cheetah parents mated with their own offspring and the resulting generations were left with very similar alleles.
describe the founder effect
Founder effect
A few individuals move to a new area and become isolated from a larger pop and might not carry all the alleles that were present in the original population (is an example of gene flow).
This means the isolated pop has less genetic diversity than the original population and deleterious recessive alleles may have a higher chance of coming together than they did the original pop.
EG: if people from a certain ethnic or religious background move and settle somewhere new and mix very little with other settlers. One person can harbour a recessive allele for Ellis van Creveld syndrome – has been common among Amish people.
what are types of selection pressures
Selection pressures
A factor that influences the survival of an individual within a population.
Competition for resources and territories
Predator-prey relationships
Competition within species for food and water
Competition within species for territories/nesting places
Sexual selection – selection of traits that successfully attacks mates.
describe natural selection
Natural selection rests on a few propositions:
Individuals differ from one another; that is, individuals within populations show variation.
Many of these variations are caused by mutations in alleles and are inheritable.
In general more offspring are born than can survive to maturity and reproduce. Because of this the struggle for existence and only some organisms can reproduce.
Some individuals have traits that make them more suited than other individuals to their viability making them better able to reproduce and pass on their alleles to the next generation.
leads to adaptive evolution
