Variation In Generations/ Evolution Flashcards
How can gene flow alter allele frequencies?
Genes can be exchanged with other gene pools as individuals move between them
How can natural selection alter allele frequencies?
Selection pressures against certain allele combinations may reduce reproductive success
How can mutations alter allele frequency?
Spontaneous mutations can alter frequencies and create new alleles
How can small population size and genetic drift alter allele frequencies?
In small populations allele frequencies can change randomly from generation to generation, alleles may be lost or fixed
How can non random mating alter allele frequencies?
Individuals seek out a particular phenotype with which to mate
What is a directional process that alters allele frequency?
Some particular alleles are favoured over others
What is genetic drift?
A mechanism of evolution in which allele frequency within a population changes over generations due to chance
What type of population is genetic drift strongest in?
Small populations
Mechanisms of genetic drift include:
- natural selection
- gene flow
- mutation
- bottle neck and founder effects
What could cause a rapid change in allele frequencies within a small population?
A major event eg. disease
What is gene flow?
The movement of genes in or out of a population (immigration or emigration)
What does gene flow result in between different populations?
Reduces differences between populations because the gene pools become more similar
What is another name for random mating?
Non assortive mating
When individuals search out mates that are most like themselves this is known as?
Assortive mating
What must occur for natural selection and evolution to occur?
- there is phenotypical variation
- some individuals have a favoured phenotype which improves chances of survival and reproduction
- over time there is a greater chance of favoured phenotype offspring being born
- the favoured phenotype will increase if selective pressures don’t change
- in time a new species may evolve
What are some ways variation can be caused?
- sexual reproduction
- mutation
- gene flow
- environmental factors
How can mutations occur?
- point/ base
- block
- whole chromosomes
What term is given to mutations that are neither harmful or beneficial?
Neutral or silent
Why are neutral mutations hard to detect?
Because they have little or no change in the phenotype
Why may neutral mutations be important in an evolutionary sense?
Even though they have no adaptive value when it occurs this may not be the case in the future
In what ways do block mutations occur?
- as a result of errors during crossing over in meiosis
- mutagens can also cause block mutations
What ways can block mutations be described?
- inversion
- translocation
- duplication
- deletion
What is an inversion block mutation?
Pieces of chromosome are flipped so their genes appear in the reverse order
What is a translocation block mutation?
Pieces of chromosome are moved from one chromosome to another
What is a duplication block mutation?
Pieces of chromosome are repeated so there are duplicated sequences
What is a deletion block mutation?
Pieces of chromosome are lost
How do whole chromosome mutations occur?
Occurs due to whole chromosomes being misplaced. Usually due to a mistake in cell division.
A mistake in meiosis is known as?
Non-disjunction
What are the two forms of non-disjunction mutations?
- aneuploidy
- polyploidy
What is aneuploidy?
A condition where one or more chromosomes are missing from or added to the normal somatic cell chromosome number
What is polyploidy mutations?
Polyploidy describes the state of having 3 or more complete sets of chromosomes
How many of each chromosome is present due to polyploidy mutations?
3 or more of EVERY one
Is polyploidy often observed in human?
It is rarely observed and is thought to be a common cause of spontaneous abortion
Gene mutations involving a single usually called?
Point mutations
What is the result of the bottleneck effect?
Only a small number of individuals remain in the gene pool to contribute their genes to the next generation
What can cause a bottleneck effect?
- seasonal climate change
- heavy predation or disease
- catastrophic event eg. Flood
What does extinction mean?
A species no longer exists and the alleles for the species have been eradicated
How can the actions of humans cause extinction?
- causing climate change
- introduction of feral organisms
- exploitation
- removing habitats
The term gene pool refers to the
Genetic makeup of a population
All the alleles within a population are referred to as …
The gene pool
New alleles arise in a sexually reproducing population by…
Mutations in DNA sequence prior to meiosis
Hominids are believed to have evolved in Africa because?
The oldest hominid fossils have been found in Africa
Why would selective breeding over many generations has produced gradual changes in farm animals?
from the restriction of breeding to chosen animals within the herd
Convergent evolution is?
Responsible for the development of analogous structures
Another name for divergent evolution is?
adaptive radiation
The measurement of the rate of accumulation of random genetic changes in the genomes of chimpanzees and humans is called?
a molecular clock
What is meant by the term ‘novel phenotype’?
a new phenotype due to a repeated gene or a change in gene expression
Any rise in incidence of antibiotic-resistant bacteria is due to?
antibiotic-resistant phenotypes being favoured through natural selection.
How is mitochondrial DNA inherited?
From the female parent
The order of first appearance of various human species, from oldest to most recent, has been shown to be?
Homo habilis, Homo erectus and Homo sapiens.
What does biological evolution involve?
Involves inherited change in a population over many generations
Two species are closely related by evolutionary descent. It may be predicted that members of these species would show the presence of?
Homologous structures
Evidence that the earliest hominins could walk erect comes from studies of their fossils. Confirmation that they walked erect came from examining?
The position of the foramen magnum on the under surface of the skull
What dating method is used for fossils less than 200,000 years?
Thermoluminescence
What dating method is used for fossils less than 350,000 years?
Uranium/ thorium
What dating method is used for fossils +- 50,000 years?
Carbon 14
What dating method is used for fossils 100-10,000million years?
Potassium/ argon
How many years does it take for carbon 14 to change to nitrogen?
5,730 years
The changing of carbon 14 to nitrogen is known as an isotopic…
Half life
Where are fossils commonly found?
Sedimentary rock, amber, tar, ice or peat bogs
What is micro evolution?
Describes the small scale changes within a gene pool over generations
What is macro evolution?
Is the term used to describe large scale changes in form, as viewed in the fossil record, involving whole species
What is phylogeny?
The evolutionary history of a species or toxonomic group
What is evolution
Permanent genetic change in a population of individuals
Putting fossils in an order of time is called?
Geological time scale
What is it called when structures have the same function in different organisms but they also come from a different origin?
Analogy
What can analogic structures indicate?
Convergence
What are vestigal structures?
Some transitional fossils have evidence of reminders of bone structures that are no longer used
What is an example of a vestigal structure?
The reduced hip and leg bone in a whale
What is a good way to reconstruct the evolutionary history of a species?
DNA hybridisation
How does the process of DNA hybridisation occur?
DNA from different species is unzipped and recombined to form hybrid DNA.
What is used to seperate hybrid DNA after DNA hybridisation?
Heat can be used and the amount of heat required to do this is a measure of how similar the two DNA strands are
How come some DNA hybrids are harder to seperate than others?
The greater the similarity of base sequence between the two strands the harder it is to seperate
How are amino acid sequences determined?
By inherited genes and differences are due to mutations
What does the distribution of species over the world indicate?
That modern forms evolved from ancestral populations and spread (radiated) out into new environments
What are the two types of evolution?
Divergent, convergent
What form evolution is the classic version?
Divergent
What is the process of divergent evolution?
An interbreeding population or species seperate into two or more descendant species resulting in once similar or related species becoming more dissimilar
What is a source of divergent evolution?
Allopatric speciation is a source of divergent evolution by creating barriers and reducing gene flow
What is a phylogeny tree?
Diagrams that show evolutionary pathways of species.
What is convergent evolution?
The occurrence of similar characteristics that have occurred in species that ave no shared DNA ie. no common ancestor
Why do similar features occur in two organisms with no common ancestor?
This is due to organisms being subjected to similar selection pressures.
Which combination of structural features is common to most early vertebrate embryos?
Gill slits, yolk sacs
The main conclusion that can be drawn from comparative embryology is that?
common structures in embryos of dissimilar species reveal common ancestry.
When compared to other apes, human have larger?
Brains relative to skull size
The founder effect and bottleneck are examples of?
Genetic drift
The out-of-Africa hypothesis proposes?
that Homo erectus evolved into Homo sapiens in Africa before migrating to other continents
How is allopatric speciation characterised?
A geographic isolating mechanism preventing gene flow
Hominins and primates both share?
Opposable thumbs
