Unit 4: AoS 2 EVOLUTION Flashcards
What is evolution?
Changes that occur in the genetic makeup of a population over time.
What is gene flow?
Gene flows is the movement of genes/alleles from one population to another as a result of reproduction between individuals from each of the populations.
What is the gene pool?
The genetic information present in a population of organisms.
What is genetic drift?
Genetic drift involves the unpredictable changes in allele frequencies in a population due to chance events.
What results in evolution?
Mutation (spontaneous, random, very rare)
Gene flow
Genetic drift
Non-random mating
Natural selection (makes a population better adapted (more fit) to its environment)
An explanation for stripes in Zebras by Lamarck VS Darwin?
Lamarck:
*A zebra is able to develop stripes for camouflage and survival against predation.
Darwin:
*There is pre-existing variation in zebras. Some zebras have prominent stripes, some don’t.
*Zebras with prominent stripes can camouflage well and SURVIVE, REPRODUCE AND PASS ON ALLELES TO THE NEXT GENERATION.
*Over time, more and more zebras will have prominent stripes.
What are the steps involved in somatic cell nuclear transfer?
1) Isolate a somatic cell and transfer nucleus from that cell to an egg cell without a nucleus (enucleated egg cell)
2) The egg cell with the new nucleus acts like a zygote which develops into an embryo.
3) The embryo is then implanted into a surrogate mother and carried to term.
What are stem cells?
Cells that have the ability to differentiate into many different specialized cells.
What are the general steps involved in therapeutic cloning?
1) Isolate stem cells (from individual or embryo)
2) Program stem cells to become desired type of cell.
3) Reinsert programmed cell into patient.
What is therapeutic cloning?
THe harvesting of stem cells to treat various diseases or replace damaged cells in the body by process of stem cell therapy.
What is reproductive cloning?
The process of creating a genetically identical organism.
What are the advantages of reproductive cloning?
- TO prevent extinction of species
- To clone livestock with high quality of meat
- TO clone animals with desirable characteristics
Disadvantages of reproductive cloning?
- Decreased variation–> may affect survival of species
- Genetic disorder passed down from donor
- Ethical concerns (ie interfering with natural processes)
- Only accessible to the rich
What is gene therapy?
- Adding functional alleles to replace defectivevalleles of certain genes, mainly targetting somatic cells.
- Can use microinjections and viruses to insert functional genes.
What are the different stem cell types and examples?
Totipotent (all) eg fertilised egg and cells of a 2,4 or 8 cell embryo.
Pluripotent (most) eg cells from inner cell mass of an early embryo
Multipotent (many) eg adult/somatic cells such as bone marrow stem cells
What is the definition of a species?
A group of organisms that can interbreed (mate) to produce viable, fertile offspring.
What is speciation?
The formation of a new species.
What is allopatric speciation?
Formation of a new species due to populations being affected by geographical isolation.
What are the steps involved in the theory of allopatric speciation?
VISCAMN.
V-VARIATION. Pre-existing genetic variation must be present in a population.
I- ISOLATION. The population is separated by a physical barrier such as a permanent river or highway –> NO GENE FLOW.
S- SELECTION PRESSURES. No gene flow between groups (ie mating/interbreeding is restricted). Different selection pressures select for different traits.
CA– CHANGE IN ALLELE FREQUENCY. Changes in allele frequencies between the two groups (genetic variation)
M- MUTATION. A mutation may occur in one group which affects their ability to mate or reproduce.
N- NEW SPECIES. When reintroduced, individuals from different groups can no longer mate or reproduce to produce viable, fertile offspring–> New species has formed.
Why would some species not be able to mater after speciation?
- Genetalia may not be structurally compatible.
- Different mating seasons.
- Different mating calls.
- Different mating rituals.
- Offspring may be infertile–> results in sterility (chromosomes are not able to be arranged in homologous pairs)
What are homologous structures?
Structures that share basic similarities but may have different functions because they evolve in different ways due to different selection pressures.
What are analogous structures?
Structures that have similar functions in organisms that are distantly related (unrelated). They are a result of adaptation to similar selection pressures.
What is the bottleneck effect?
Definition VCAA: A severe reduction in genetic diversity due to a chance event (catastrophe) that may change allele frequencies.
A bottleneck effect results from the reduction in size of a population, typically by a natural disaster, such that the surviving population is no longer representative of the original population.
What is the founder effect?
The founder effect is an example of genetic drift caused by the colonisation of an area by a limited number of individuals from a parent population, not representative of the original population.
What is an adaptation?
Structural, biochemical or behavioural characteristic that assists an organism to survive and reproduce in its environment.
What does Charles Darwin’s theory of evolution state?
1) individuals in a population possess different genotypes and therefore different phenotypes
2) the struggle for survival occurs in populations due to selective pressures
3) the best suited phenotypes produce more offspring. Variations are inherited and therefore each new generation will contain proportionally more of the favourable phenotype.
4) over time, the new variations are so distinctive from the original population that a new species has evolved.
What is divergent evolution?
The process by which an interbreeding population or species separates into two ore more descendant species, resulting in once similar or related species becoming more and more dissimilar due to different selection pressures.
What is convergent evolution?
Convergent evolution is when two species, which do not share a recent common ancestor, independently develop similar features due to similar selection pressures.
Describe the process of binary fission.
Bacteria reproduce asexually by binary fission. The single, circular chromosome that is attached to the cell membrane in bacteria is copied and then the cell membrane and cell wall expand separating the chromosomes. The cell membrane and cell wall then grow down between the two chromosomes creating two genetically identical daughter cells.
What is mitosis?
Mitosis is the nuclear division of one cell into two genetically identical daughter cells i.e. each daughter cell contains the same number of chromosomes as the original parent cell.
What is the purpose of mitosis?
It ensures that cells maintain a large surface area to volume ratio and allows for:
- growth of an organism
- replacement of cells which have died or been damaged
What is meiosis?
Meiosis is a reduction division involving one diploid parent cell dividing to produce four haploid daughter cells that are genetically varied, i.e. each daughter cell has half the number of chromosomes of the parent cell
What is independent assortment of chromosomes in meiosis and at what stage of meiosis does it occur in?
Maternal and paternal chromosomes of each homologous pair line up independently of all other homologous pairs along the equator of cell during metaphase I of meiosis. This is an important source of genetic variation within a species.
What is crossing over in meiosis and at what stage of meiosis does it occur in?
During prophase I, homologous chromosomes pair up and often make contact with one other, becoming intertwined. During this time, a section of the genetic material on a maternal chromatid can be swapped for the corresponding genetic material on the homologous paternal chromatid. The point of crossing over is called the chiasma and can lead to new combinations of genetic material on a chromosome, referred to as recombination.
When does non- dis-junction occur and what is/are the result of it?
Failure of chromosome pairs to separate during Anaphase I or Anaphase II
- If single chromosomes fails to separate (Down Syndrome, Kleinefelter’s, Turner’s) the event is anueploidy (older mother= greater chance of aneuploidy)
- If a complete set of chromosomes fails to separate, event is polyploidy (not viable in humans but viable in plants)
What is natural selection?
Selection that results in “survival of the fittest”. A fit organism is one that is better adapted to the environment.
Key points to remember in natural selection questions?
VESIG. Variation- pre-exisiting variation (what type of variation is present in the population?) Environment (What is the environment like? How does this contribute to selection pressures?) Selection pressures (Selective agent/ selective advantage) Inheritance (variation must be inherited; that is, individuals survive, reproduce and pass on alleles to the next generation Generations (What do you expect to happen to the frequency of the alleles over generations?)
What are the evidences in support of Darwinian evolution?
BADFEW.
Biochemical similarities exist between organisms of recent common ancestry.
Anatomy (structural) similarities exist between organisms of recent common ancestry
Distribution (biogeography) of present day organisms reveals many cases of common ancestors, once separated, evolving into different species (e.g. under influence of continental drift)
Fossil records reveal gradual changes in organisms from ancestral forms over time e.g. transitional fossils
Embryology comparisons
Witness of the process of change in living organisms, via natural selection or artificial selection.
What is a vestigial structure?
- Organs that are have no particular function or are reduced in nature.
- They indicate that a role previously existed for functional forms of these organs in the ancestors of the present day organism
What are the different types of chromosomal (block) mutations?
- Deletion
- Inversion
- Translocation
- Duplication