chapter 9 (evolution) Flashcards
(37 cards)
1
Q
genetic diversity
A
- the variation in genetic makeup or allele within a population
- larger, more diverse pool with a greater variety of alleles will lead to a greater number of genotypes and phenotypes therefore resulting in a greater genetic diversity.
2
Q
point mutation
A
- a mutation that alters a single nucleotide in a DNA sequence
3
Q
silent mutation (substitution)
A
- DNA triplet codes for the same amino acid
- single base substitution
- may have no effect
4
Q
missense mutation (substitution)
A
- codes for a different amino acid, alters polypeptide
- could alter functioning
- lesser impact on the end/non-critical part
- greater impact in the middle, may cause protein to be non-functional
5
Q
nonsense mutation (substitution)
A
- ends translation/mutated triplet and becomes stop codon
- stops protein production
- most dangerous
6
Q
frameshift mutation (insertion)
A
- single base substitution (major affect)
- codes for different amino acid
- all codons are shifted one spot
7
Q
frameshift mutation (deletion)
A
- reading frame is shifted from deletions
- all triplets downstream will code for different amino acids
- proteins become non-functional
8
Q
block mutation
A
a mutation that affects a large chunk of DNA, or a entire gene
9
Q
duplication
A
- large or small section is copied
- increase in trinucleotide repeats
- results in the addition of many more amino acids in resulting protein
- protein function can be altered
- (e.g Huntington’s Disease)
10
Q
deletion
A
- portion is removed or lost
- chromosomes breaks in 2 places and rejoins leaving a piece out
- large deletions are usually lethal
- smaller deletions lead to genetic disorders
11
Q
translocation
A
- segments of 2 chromosomes are exchanged, attaches to different non-homologous chromosomes
- if parts are lost it has no effect on carrier but can affect the gametes
- zygote receiving extra copy of DNA
- (e.g Down Syndrome)
12
Q
inversion
A
- segment is removed then replaced in the reverse order (flipped)
- depending on where break occurs
- if in coding or promoter region gene function is lost.
13
Q
environmental selection pressures
A
predation, disease, competition, climate change
14
Q
four conditions of natural selection
A
- variation: individuals population vary genetically which leads to phenotypic differences
- selection pressure: an environmental selection pressure impacts the survivability of organisms within a population and their ability to reproduce
- selective advantages: individuals with phenotypes that are fitter or more advantageous under the environmental selection pressure are conferred a selective advantage allowing them to survive and reproduce more successfully
- heritability: the advantageous trait must be heritable, allowing it to be passed on from the parents to their offspring therefore over time the frequency of the advantageous allele will increase.
15
Q
Darwin’s observations
A
- 1: there is a phenotypic variation within species
- 2: offspring tend to inherit traits of their parents
- 3: species produce more offspring then required to replace themselves
- 4: there is a struggle to survive.
16
Q
Darwin’s inferences
A
- A. Individuals whose traits give them more chance to survive and reproduce leave more offspring than other individuals
- B. The unequal chance of reproduction will lead to accumulation of favourable traits in the population over generations.
17
Q
sexual selection (female choice)
A
- who reproduces at the expense of survival
- males fight with each other in order the get the right to mate with all the females
18
Q
bottleneck effect
A
- The bottleneck effect occurs when a large portion of a population is wiped out by a random event such as a natural disaster
- New generation will depend on remaining alleles
- decreases genetic diversity
19
Q
founder effect
A
- The founder effect occurs when a small unrepresentative sample of individuals separates from a larger population to colonise a new region and start a new population
- decreases genetic diversity
20
Q
immigration
A
- the movement into a population
- alleles are added to the gene pool of a population
- increase genetic diversity
21
Q
emigration
A
- the movement out of a population
- alleles are removed from the gene pool of a population
- decrease genetic diversity
22
Q
interbreeding
A
- when two individuals living in different populations mate and have offspring
- increase genetic diversity
23
Q
Reductions in genetic diversity have two major risks
A
- Inbreeding: this keeps harmful alleles in the gene pool
- Lower adaptive potential: populations become vulnerable to new selection pressures that could challenge and potentially wipe out the entire population due to the absence of advantageous alleles.
24
Q
Speciation
A
- is the process by which populations genetically diverge until they become distinct species
- Individuals are recognised as different species if they can no longer interbreed with one another to produce viable and fertile offspring.
25
Hybrids
- They can all mate and produce offspring, but the offspring are infertile
e.g Horse and Donkey create a Mule
26
isolating mechanisms (pre-reproductive)
- Geographical - individuals may not be able to interact with each other due to separation by barriers (e.g. body of water)
- Ecological - individuals may inhabit different ecological niches or habitats so they do not interact with each other
- Temporal - the time of the day or year when individuals are ready to breed may differ
- Behavioural - the type of mating behaviours, such as mating call, of individuals may vary.
- Structural - the physical characteristics of individuals may drastically vary, physically preventing breeding.
27
isolating mechanisms (post reproductive)
- Gamete mortality - the sperm may be unable to penetrate the ovum for fertilisation
- Zygote mortality - fertilisation may occur and a zygote may be formed, however, it will not survive
- Hybrid sterility - a viable offspring may be formed and may survive until adulthood, but will not be fertile.
28
allopatric speciation
- the geographic separation of a population from a parent population resulting in the formation of a new species
- 1 A geographical barrier separates a population preventing gene flow.
- 2 Different selection pressures act upon each population favouring different phenotypes and allowing for genetic differences to accumulate.
- 3 Eventually, sufficient genetic differences accumulate so that the two populations can no longer interbreed to produce viable and fertile offspring,
- (e.g galapagos finches, due to all bring in different ecological niches on the different islands they were all faced with different selection pressures, experienced adaptive radiation)
29
sympatric speciation
- the divergence of a species from an original species without the presence of a geographical barrier sympatric, speciation occurs within populations sharing the same geographical location
- different selection pressures act on different phenotypes within a population causing them diverge and create a new species
- also arise from genetic abnormalities that occur during gamete formation resulting in a different number of chromosomes compared to the parents.
- (e.g howea palms, different PH levels were the reason for their speciation, these changes altered their flowering time and therefore they could no longer interbreed)
30
selective breeding
- the changing of a population's gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait
31
the requirements for selective breeding
- Variation: individuals in a population vary genetically, which leads to phenotypic differences
- Selection pressure: direct human intervention places an artificial selection pressure upon a population of individuals only allowing certain individuals with desirable traits to breed together
- Heritability: the trait selected must be heritable allowing it to be passed on from the parents to their offspring.
32
effect of selective breeding on genetic diversity
- restricting breeding to these individuals the generational increase in the frequency of the selected allele will decrease genetic diversity as the phenotypes of the population are driven towards a specific allele
33
natural selection
- population is in the wild, depends on selection by the environment
- selecting agents: climate changes, competition, food shortages, mate availability, predator abundance, pollution
34
artificial selection
- population is in captivity, occurs when humans deliberately select particular pants or animals to breed for a specific trait
- select breeds that would not be genetically fit in the wild
35
antibiotic resistance
- bacteria with resistance to a particular antibiotic are present confer a selective advantage allowing them to continue leaving and replicating increasing the allele frequency for antibiotic resistance
36
antigenic drift
- involves small and gradual changes in the genes encoding for viral surface antigens
- as mutations continue to accumulate a new subtype can firm which will no longer be recognised
37
antigenic shift
- involves sudden and significant changes in the genes encoding for viral surface antigens
- two or more different strains of a virus combine
- natural immunity is uncommon making it extremely infectious
