EVOLUTION Flashcards
Define Evolution
changes in the genetic composition of a population over time.
Darwin was trying to explain three key observations;
adaptation, unity and diversity.
Define adaptation
the fit between an organism and the environment or the striking way that organisms appear to be suited for living in their environment.
Explain the concept of unity and diversity
That is the organisms and species have many shared characteristics (unity) but at the same time there is rich diversity.
The Greek philosopher, Plato (427–347 BC) viewed species as
immutable ‘types’.
earthly forms were simply imperfect copies of a transcendental ideal.
Explain Essentialism
Essentialism saw natural variation as noise that had to be filtered out in order to describe the true form of a species.
What did Aristotle do?
made the first serious attempt to classify animals on the basis of their anatomy.
Aristotle thought that species could be arranged on a ladder of increasing complexity later called the Scala Naturae (scale of nature). Each species having an allotted run on the ladder.
What did Linnaeus do?
Linnaeus founded modern taxonomy by developing the system of Latin binomial nomenclature, e.g. Homo sapiens.`
Explain Gradualism
Gradualism argues that profound change is the cumulative result of slow, continuous processes.
What are The 4 principles of natural selection?
- Individuals within populations are variable, in terms of their morphology, physiology, and behaviour (variation).
- The variation among individuals are, at least in part, passed from parents to offspring (heritable).
- In every generation some individuals are more successful at surviving and reproducing than others (differential survival).
- The survival and reproduction of individuals are not random; instead they are tied to the variation among individuals. The individuals with the most favourable variation are selected (selection).
Of Darwins two claims, which is fact and which is a theory?
That species evolve is now an accepted fact (pattern). The mechanism (process) that Darwin proposed for adaptive evolution – natural selection – is a theory.
Define homologous structures
species that have structures that have underlying similarities yet quite different functions.
e.g. The mammalian forelimb preforms quite different functions but are constructed from the same elements.
Define vestigial structure
A vestigial structure is a functionless or rudimentary version of a body part that has an important function in other closely related species.
e.g. The North Island brown kiwi, Apteryx mantelli, is a flightless bird but still has a tiny stubby wing.
What is Biogeography?
Biogeography is the scientific study of the geographical distribution of species.
What are theories?
Theories are conceptual frameworks with explanatory power supported by many lines of evidence.
What is microevolution?
Change within a species
Is natural selection the only mechanism of evolution?
no
What is an example of artificial selection?
selective breeding
HOW DID S. aureus strains become resistant to methicillin
S. aureus strains exhibited variation and some strains could synthesise their cell wall with a different protein not affected by methicillin.
How did bacteria destroy penicillin?
By producing the enzyme penicillinase.
What is macroevolution?
Differences between different species.
homology can be seen in
morphological, genetic or behavioural characteristics.
Explain the 18th century theory of blending inheritance
Blending inheritance was the idea that features in the child resulted from combining or blending qualities of both parents, this was thought to occur in the blood.
This hypothesis predicts that over generations a freely mating population will give rise to a uniform population of individuals.
What did the blending hypothesis fail to explain?
The blending hypothesis fails to explain the reappearance of traits after skipping a generation.
Define Polygenic inheritance
– mode of inheritance in which the additive effect of two or more genes determines a single phenotypic character.
How many genes are speculated to control human skin colour?
at least three separate genes
Define population
A population is a group of individuals of the same species that live in the same area and interbreed.
Define the gene pool
the sum of all the alleles of all genes of all individuals in the population.
What is meant by the term fixed allele?
If only one allele exists at a particular locus or gene in a population, the allele is said to be fixed.
What is the Hardy-Weinberg equations?
p + q = 1
p^2 + 2pq + q^2 = 1
What are the Conditions for Hardy-Weinberg?
1. No mutations.
- Mating occurs at random.
- No natural selection.
- Extremely large population size.
- No gene flow
In the Galapagos Islands, what happened when there was a drought to the seeds available and also the beaks of the birds?
Seeds in abundance were large hard seeds, and only finches with large deep beaks could crack them open, therefore directional selection occurs for larger beaked finches.
Explain the Biological species concept
a group of organisms that actually (or potentially) interbreed in nature, producing other reproductively viable offspring, and are reproductively isolated from other groups.
What type of mutations are the most common?
silent mutations
What is Haemophilia?
Haemophilia A & B are X-linked recessive disorders caused by nonfunctional / absence of certain blood clotting proteins.
Define genetic drift
Genetic drift is the change in allele frequencies as a result of chance events.
The overall affect of drift is a loss of
genetic variation
What is the founder effect?
Founder effect results when a small population branches off from a larger one, by chance the small population may not have all the alleles present in the larger population.
What is a population bottle neck?
Population bottlenecks occur when a population is drastically reduced in numbers, consequently chance effects can result in the loss or fixation of alleles.
Define gene flow
Gene flow is the movement of alleles into or out of a population due to the movement of individuals or their gametes.
Mutations in which type of cells affect the gene pool?
ONLY in gametes.
Define Natural selection
Natural selection is the process in which individuals with certain heritable traits survive and reproduce at a higher rate than those without the traits.
Does natural selection act on genotype or phenotype?
Selection acts on the phenotype (trait) not the genotype; it can act only indirectly on the genotype.
In terms of genetics, selection results in changes in
gene frequencies from one generation to the next.
Darwinian fitness refers to
the ability to survive and reproduce, it considers both viability and fecundity.
What does survival of the fittest depend on?
the individual and the conditions of the current environment
e.g. the fittest individual during an ice age is probably not the fittest individual once the ice age is over
Define Absolute fitness (W)
a measure of the total number of offspring an individual produces.
Define Relative fitness (w)
is the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals.
What are the three types of natural selection?
Directional selection
disruptive selection
Stabilising selection
Explain directional selection
Directional selection occurs when one of the extremes is favoured, driving the population in a particular direction.
Directional selection is common when an environment changes or when individuals move to a new environment.
Explain disruptive selection
Disruptive selection occurs when the extreme phenotypes are selected at the expense of intermediate forms.
Explain stabilising selection
Stabilising selection acts against both extreme phenotypes and favours intermediates.
Explain sex selection
Sexual selection is argued to result in sexual dimorphism in some species (differences in size, colour, ornamentation and behaviour).
Explain Intrasexual selection
individuals of the same sex competing directly, and is thought to occur between males in many species.
Explain Intersexual selection
Intersexual selection or mate choice, occurs between different sexes, and is typically argued to occur when females select mates.
Explain the heterozygote advantage
Heterozygote advantage occurs when individuals that are heterozygous have a greater fitness than do either kind of homozygote.
Give an example of the heterozygote advantage
Heterozygotes for the sickle-cell allele are protected against the severe effects of malaria, a disease cause by a unicellular parasitic eukaryote.
Explain Frequency-dependent selection
In frequency-dependent selection, the fitness of a phenotype depends on how common it is in a population.
Define Exaptations
Exaptations are the complement of adaptations, as they are traits that have been co-opted or enlisted for a new use.
Define species
Species are defined in terms of reproductive compatibility
What is a limitation of The biological species concept?
It doesn’t apply to asexual organisms e.g. prokaryotes.
Explain the Morphological species concept:
It distinguishes a species based on body shape and size.
Explain the Ecological species concept,
It defines a species in terms of its ecological niche.
Explain the Phylogenetic species concept,
It defines a species as the smallest group of individuals that share a common ancestor.
Explain the Specific mate recognition species concept,
defines a species as a group of organisms that share a common mate recognition system.
Explain Allopatric speciation
Allopatric speciation occurs when gene flow is interrupted as a result of a population being divided into geographically isolated subpopulations.
What is considered to be the most common mode of speciation?
allopatric speciation
What is Vicariance?
Vicariance occurs when a population is isolated due to the formation of a physical barrier e.g. mountain range or ocean.
How can sympatric speciation occur?
Sympatric speciation can occur via polyploidy, sexual selection and habitat differentiation.
Define Polyploid organisms
Organisms containing more than two paired (homologous) sets of chromosomes.
Polyploid speciation is common in
plants (but rare in animals)
Define Anagenesis
Anagenesis is gradual change within a single lineage over time.
Define Cladogenesis
Cladogenesis is evolutionary change produced by the branching of populations to form new species.
Define Adaptive radiation
Adaptive radiation is the rapid formation of many new species from a single ancestral group, characteristically to fill a new ecological area / zone.
Explain the difference between gradualism and punctuated equilibrium models
In gradualism species diverge slowly and steadily over time, in contrast in a punctuated model new species change most at the time of speciation and then change little.
Why can natural selection not produce ‘perfect organisms’?
o Selection can only act on existing variation (on the existing alleles that are present in the population)
o Evolution is limited by historical constraints (i.e. you only evolve existing features e.g. the wing is simply a modification of the forelimb, not its own structure)
o Adaptations are often compromises (not all individuals contain all the desirable traits e.g. sexual vs natural selection in peacocks – the bugger and vibrant peacock may attract more females but also may attract nor predators)
o not all evolutionary change is adaptive e.g. genetic drift
o chance, natural selection and the environment interact
What is an example of exaltation?
Feathers in birds were present in flightless animals as its original selection was due to thermal insulation and perhaps ornamental features, but is now used for flight.
What are cryptic species?
They are organisms from different species that look as if they are from the same species e.g. forest elephant vs the savanna elephant
Why doe we agriculturally produce more polyploid fruits?
The larger number of chromosomes is often associated with a larger size of the fruit or grain, e.g. bananas and the bread wheat grain are both polyploids.
Define Taxonomy
Taxonomy is the discipline of naming and classifying (grouping) organisms.
Does The placement of species into orders, classes and so on reflect evolution history?
no not necessarily.
What is the difference between taxonomy and systematics?
In today’s usage, taxonomy deals with discovering, describing and naming organisms.
Systematics deals with the phylogenetic relationships between taxa, especially at the higher levels.
These days systematics is greatly influenced by data derived from DNA of the nuclei, mitochondria and chloroplasts – molecular systematics.
What does a phylogenic tree show?
Phylogenetic trees show the pattern of decent NOT phenotypic similarity
What is the difference between anagenesis and cladogenesis?
Anagenesis change is gradual, apparently directional change within a lineage while cladogenesis is the branching episodes of speciation.
Define cladolistics
Cladistics represents relationships as a series of branching events, that are determined by shared derived characters.
Define a clade
A clade is a group which includes an ancestral species and all of its descendants.
What is a basal taxon in a phylogenic tree?
the organism that is the first one to branch off the tree
What is a monophyletic group?
All organisms in this group have a common ancestor
What is a paraphyletic group?
it does not include all the descendants of the common ancestor
What is a polyphyletic group?
it does not include the most recent common ancestor of all the organisms in this group
What are the three stages taken up y the Genome project?
linkage mapping, physical mapping and DNA sequencing.
Explain whole genome shotgun sequencing:
DNA is cut into overlapping fragments short enough for sequencing
Clone the fragments in plasmid or other vectors
sequence each fragment
Order the sequences into one overall sequence with computer software
How many chromosomes in the human genome?
46 chromsomes
What makes up majority of the human genome?
non coding regions (introns)
ARE GENES EVENLY DISTRIBUTED? e.g. the number of base pairs allocated to each gene the same
no
What is Bioinformatics?
Bioinformatics is the application of computational methods to the storage and analysis of large biological data sets.
Order the following in terms of genome size:
Archaea, Bacteria and Euklaryotes
Bacteria
Archaea
Eukaryotes
(Eukaryote genomes tend to be larger than Prokaryotic genomes)
Is there a relationship in eukaryotes between genome size and phenotypic complexity?
No
