Evolution Flashcards
Gene pool
The sum total of genetic information present in a population
Selective pressure
Environmental conditions that favour certain individuals
Selective advantage
Organisms that have better phenotype to survive will have more likely survive and pass them onto the next generation
Is it easier for natrual selection to get rid of a dominate or recessive trait
It’s easier to get rid of a dominant trait due to heterozygous Bb have the same selective advantage as BB and when having offspring there is still always a chance for the recessive trait to occur.
What is gene flow
Also known as migration
Changes due to migration can occur very quickly
Is directional
What’s genetic drift
Is a pattern of random change in allele frequency from one generation to the next
the direction of change is UNPREDICTABLE.
Unlike natrual selection it does not favour one allele over another
Mainly occurs in small populations
What is genetic bottle neck
When the size of population is drastically reduced from a bush fire, flood, new disease etc.
The few survivors that reproduce to give the next generation may be an underrepresented sample of the original gene pool
What’s the found effect
When a small underpresentative or nonrandom sample of the population leaves to colonies a new region.
The first organisms of the population to start a new colonie are called founders
What’s a mutation
New alleles occurring due to mistake in DNA
Whats point mutation
Affects a single base in DNA
by substitution
Commonly affect structural genes
What’s a frameshift mutation
A three nucleotide (codon) insertion or deletion cause the genes message it encodes to no longer make sense
What’s a block mutation
Chromosomal change affecting large segments of a chromosome
Either:
Deletion of part of a chromosome
Duplication or gain of part of a chromosome
Translocation or reciprocal exchange between non homologous chromosomes
Inversions when a segment of a chromosome rotates through 180 degrees
What’s aneuploidy
The presence of an abnormal number of chromosomes eg a human cell contain 45 or 47 chromosomes
What’s polyploidy
When a cell contains more than two sets of chromosomes
Define natural selection
A process by which new heritable traits of organisms better adapted to their environment tend to survive and produce more offspring
What’s the steps of natural selection
- There is variation between individuals
- Organisms with favoured phenotype will have an improved chance of survival and reproducing.
- individuals who survive and reproduce increase the chances of passing those genes on to the next generation
- favoured genes will increase in frequency within the population over time
- over long period of time the characteristics of the favourable gene will be the most noticeable within the population
Why can’t organisms produced asexually not undergo natural selection
They do not have variation between individuals
Living factors of selective pressures
Predators , competing for food, water, space, mates, parasites
Non living facfors of selective pressures
Changes to temperature, pollutants, availability of water, minerals, light and natural disasters
Define biological species
A group of interbreeding individuals, they are often composed of different populations that are quiet distinct these are known as subspecies.
What does speciation mean
Refers to the process by which new species are formed
It occurs when gene flow has ceased between populations where it previously exists
Is brought about by development of reproductive isolating mechanisms which maintain the integrity of the new gene pool
What’s the two types of speciation
Splitting and budding
What’s splitting speciation
A species could split fairly equalling into two populations that envolve differently until they eventually become separate species
Photo
What is budding speciation
A small part of species population could “bud off” from main part and evolve rapidly to form a new species while leaving most of the original species population unchanged
Photos
What is allopathic speciation
Populations become geographically separated and become subjected to different selection pressures. They establish reproductive isolating mechanisms in isolation.
Step 1 of allopathic speciation
Moving into new environment
The population occupies new parts of the environment
The population has a common gene pool that interbreed
Step 2 of allopatric speciation
Geographical isolation
Gradual formation of physical barriers may isolate parts of the population at the extremes of the species range
The gene flow between the isolated populations is prevented and becomes rare
Agents causing geographical isolation include
Continental drift, climate change and changes in sea level
Step 3 of allopatric speciation
Formation of subspecies
Isolated populations have different selection pressures that will favour the individual traits suited to each environment
Natural selection occurs
What’s atage 4 of reproductive isolation
Each sub species develops reproductive isolating mechanisms
Even if geographical barriers are removed the species will no longer breed with each other
What is artificial selective/ selective breeding
Involves breeding (selecting) from individuals with the most desirable phenotype. Selection imposed by humans is more intense and rapid then occurring in nature
How does artificial/ selective breeding occur
Artificial insemination, embryo transfer,
Does Loss of genetic variation matter
When a disease occurs if all the species are the same they will die out eg when the potato famine occurs one million Irish pease te died due to not having enough potatos to feed on.
Variation is needed if the environmental conditions changes
What are scientists doing to stop a disease in crops destroy everything
The keep seed banks and gene banks that seek to conserve diversity in plant species
What are fossils
Any parts or impressions of an organism that may survive after death
When do fossils form
Only under special conditions:
Anything from water has more chance of forming a fossil
Fossils form best when organisms are buried quickly as it slows the decay process
What types of rocks are fossils most commonly found
Sedimentary rock
What’s a fossil rock profile
Layers of sedimentary rock arranged in the order they were laced down. The most recent layers are near the surface
Define evolution
Permanent genetic change in a population of individuals over an extended period of time
Does not refer to changes occurring to individuals over their own life time
What’s the two types of evolution and explain
Micro evolution- describes small scale changes which gene pools over generation
Macro evolution- large scale changes in form as viewed in the fossil record involving whole groups of species.
Index fossils
Fossils used to identify geological periods
Transitional fossil
Fossils that are intermediate between ancestral and descendant species.
They show evolutionary transition
What’s absolute dating
If a fossil can be accurately age then it is easier to form accurate time of life
Radiometric/ isotopic dating
More accurate way of dating fossils. The method measures the amount of isotopes that are radioactive in either the fossil or rocks the fossil is found in
What’s radio carbonate dating
Used to identify the age of young fossils.
Carbon is found in dead remains of organisms. Most of carbon is non radioactive carbon 12 while a small amount is in form of carbon 14 is radioactive.
Carbon 14 breaks down into nitrogen 14
Carbon 12 will not break down
By comparing the amount of carbon 14 with nitrogen 14 you can get a more accurate age
The diagram for radio carbonate dating
Photos
Homologous structures
Structure in different organisms that have a similarities present as a result common ancestory.
Even though they may serve a different function as they have been adapted for a different purpose.
Eg wing, arm, leg etc
This provides evidence for divergent evolution
Anologous structures
Have similarities between species but is not inherited from a common ancestor
Structures that have the same function in different organisms may come from different origins
Eg wings on birds and butterflies
May indicate convergence evolution
What is DNA hybridisation used for
One way to reconstruct the evolutionary history of species
What is the process of DNA hybridisation
DNA from two different species is unzipped and recombined to form hybrid DNA
Heat is used to separate the hybridised strands
The amount of heat required to do this is a measure of how similar the DNA strands are (%bonding)
More heat required displays that there are more bonds equalling DNA to be similar
Less heat required for very different species
Amino acid sequencing in evolution history
Closely related species have proteins with similar amino acid sequences
The degree of similarity of these proteins is determind by the mutations that have occurred.
The greater the time since common ancestry= more mutations
What is divergent evolution
When closely related species become more dissimilar over time usually in response to different environmental conditions and selection pressures
What’s an example of divergent evolution
Galapagos island finches
Natural selection occurred resulting in different species of birds changing to suit the foods they eat on the islands
What is convergent evolution
Occurs when similar features develop independently in organisms that are not clearly related but may live in similar environments.
Eg a wolf ang tiger
What’s a mass extinction
A period in the geologic history of the earth during which an abnormally high number of species die out over a relatively short time frame
What is mitrochondrial DNA
Another piece of evolutionary evidence
MtDNA inherited from the mother only
By comparing mtDNA in populations it is possible to trace the origin of mtDNA to a female ancestor in Eastern Africa called mitrochondrial eve
Gene regulation and natrual selection
Two important genes in Darwin finches
BMP4 a regulatory gene- this gene stimulates the production of material that makes beaks
CAM-a gene that regulated calcium that makes the shape of the beak
When BMP4 is turned on early the CAM gene is turned on late then a short break occurs
What’s the molecular clock do
Uses mutation rates in DNA to estimate the time two species split and evolve independent
What does the molecular clock theory rely on
The Mutations are neutral, they do not affect phenotype
The mutations occur at a fairly regular Occassion
What does each degree below 87 degrees represent in DNA hybridisation
The percentage of difference in the DNA
What’s the first group of organisms that show human features
Primate- advanced group of mammals that share common characteristics
Characteristics of primates
Vision- large forward facing eyes with 3D vision
Face- snout is reduced and sense of smell also
Collarbone-ability to rotate the arm so it can extend behind the body
Posture- upright and erect posture at times
Hands-opposable thumb
Reproduction- maternal instincts exist
Social organisation- live in groups
What’s hominoids
Grouping of greater and lesser apes including gorillas, chimpanzee and humans
What’s a hominins
Modern human species and our extinct close relatives that could walk erect on their hind legs in a sustained fashion
What happened to the foraminifera magnum over time
Moved further forward so the skull is balanced on the spine
What’s cultural evolution and examples
Changes in human societies over time where those changes are socially passed on and not genetically Eg domestic animals Burials and rituals Totems Paintings
What’s technology evolution
Development of technology that gives humans increased control over their environment. It has increased at an exponential rate. The rapid increase of tools is directly related to cultural evolution and increase in brain size
Human evolution 5 significant developments over 5 million years
- Hind limbs become longer so forelimbs no longer drag
- Stance progressively became upright due to change in position of foramen magnum
- The brain capacity increase=increase intelligence
- The size of jaw decreased
- Thumbs became fully opposable. Toes straighten and arc develops in feet
What’s the out of Africa model
Homo sapiens sapiens have common origin in Africa. Members from Africa migrated out. Supported by mitrochial DNA
What’s classified as a young fossil
40,000-50,000 years old
What causes antibiotic resistance
Any mutation that provides an advantage under certain selection presses may spread quickly through bacteria population
This has created the selective environment for increased frequency of antibiotic resistance genes in populations
Relative dating vs absolute dating
Absolute dating is the exact age of a fossil eg
Relative dating is the relation of age compared to rock layers around it eg the fossil position in the layer of rocks
