Relatedness of Species (chapters 9-10) Flashcards
Allele
Alternate form of a gene
Gene Pool
All possible alleles at all gene loci of a popularion of a single species at a time
Spontaneous Mutation
Mutation occurring for no particular reson
Induced Mutation
Mutation caused by ionising radiation or a chemical mutagen
Mutation
Unpredictable or random change to DNA of an organism
Cannot be predicted what gene will be affected
Most mutations have NO EFFECT on organisms
Chemical Caused Mutation
Mutations caused by chemicals which interact with DNA
eg. Heavy Metal Can:
- Cause sugar phosphate backbone to break
- Inhibit enzumes which repair DNA
Block Mutations
Block mutation involved more than a single gene
Include inversions, deletions, duplications and translocations
Point Mutations
Mutation at the nucleotide level
Normally involves change to a single nucleotide
eg. Single base substitution
Single Base Substitution - Missense Mutation
Substitution mutations which code for a different amino acid, altering the primary
structure of the polypeptide.
Single Base Substitution - Addition Mutation
Extra base added
Single Base Substitution - Nonsense Mutation
Substitution mutations which prematurely end the translation of a gene’s mRNA.
- Creates stop codon
Single Base Substitution - Silent Mutation
Substitution mutations that have no effect on the resulting amino acid sequence.
Due to the degenerate nature of the genetic code
Single Base Deletion
Point Mutations that cause a frameshift mutation
Frameshift Mutation
Addition or deletion of one or two nucleotides, which alters the reading frame of all the following nucleotides
Substitution Mutation
Single nucleotide exchanged for different nucleotide
Phenotype
Physical, Expressed
Genotype
The genetic makeup of an individual organism
Environmental Selection Pressures
External agents influencing species ability to survive
- Facilitate mechanisms of natural selection
- Abiotic or Biotic
eg. Predation, Disease, Competition
Impact of Selection Pressures
Some phenotypes have advantages over others when it comes to survivability or reproducability
Leads to change of allele frequency over time
Very slight differences in survival rate can have big differences on allele frequency
eg. In dense rainforests, plants need large surface area to photosynthesize
- Plants with allele for larger surface area more likely to survive
- More likely to reach next generation
Selection Pressure Questions (x3)
- What is the selection pressure?
- What is the advantageous phenotypical trait?
- What is the advantageous allele?
Natural Selection
Process whereby members of a population that are better sorted to environment are more likely to survive and pass traits on to next generation
- beneficial traits become more ocmmon in population
- biodioversity decreases as a result
- ‘survival of the fittest’
Four conditions of Natural Selection
1) Variation
2) Selection Pressure
3) Selective Advantage
4) Heritability
Natural Selection Condition - Variation
Individuals in a population vary genetically, leading to phenotypic differences
Natural Selection Condition - Selection Pressures
Environmental selection pressure impacts survivability of organisms and ability to reproduce
Natural Selection Condition - Selective Advantage
Individuals with phenotypes that are advantageous under environmental selection pressure are conferred a selective advantage
Natural Selection Condition - Heritability
Advantageous traits must be heritability, allowing to be passed from parent to offspring
Overtime advantageous allele will increase
Genetic Diversity
Measures of genetic variation within species/population
- high genetic diversity helps maintain the health of a population
- provides flexibility to adapt
Lack of Diversity
Example: Irish Potato Famine
- deadly blight caused severe famine
- only 1 species of potato was grown, no ability to adapt to blight
- due to lack of diversity
Sexual Selection
Where selection pressure is ability to find mate
For some species, natural selection favours individuals who reproduce at risk of survival
Block Mutation - Deletion
When part of DNA molecule not copied in DNA replication
Can be as small as single nucleotide or as big as entire chromosome
eg. Turner Syndrome
Block Mutation - Duplication
Piece of DNA abnormally copies one or more times
May alter protein function
Block Mutation - Inversion
Portion of chromosome breaks off, flips, then reattaches
Genetic material inverted
Block Mutation - Translocation
Portion of one chromosome transferred to another chromosome
Two Types:
- Reciprocal Translocation
- Robertsonian Translocation
Reciprocal Translocation
Segments from different chromosomes exchanged
Robertsonian Translocation
Entire chromosome attached to another centromere
Genetic Drift
Change in allele frequency in gene pool due to random chance
Genetic drift only ever has significant effect on alelle frequency in gene pool of small population
- bottleneck > decreases diversity
- founder > decreases diversity
Founder Effect
the reduction in genetic diversity that occurs when a population is derived from a small unrepresentative sample of the original population
Genetic Bottleneck
Genetic drift where frequency of alleles is changed due to a near extinction event
= reduced genetic diversity
eg. Galapagos Finches
- El Nino Monsoon - decimated large food sources on islands
- Lack of larger seads, growing vines caused lots of small seads
- Large beaked finches struggled to reach small seads, many died
Gene Flow
Transfer of genetic information from one population to another by migration
Movement of individuals can introduce new Alleles or change Allele frequency in population
- If population is not isolated
- Breeding between populations of some species
- Causes Mutations
- Increases genetic diversity
- Immigration > increases diversity
- Emigration > decreases diversity
Unrepresentative
Doesn’t represent all alleles
Factors increasing diversity (x3)
- Mutation
- Sexual reproduction
- Gene flow
Factors decreasing diversity (x3)
- Natural selection
- Gene flow
- Genetic drift
> Founder effect
> Bottleneck effect
Biological Concept of Species
A group of living organisms consisting of similar individuals that actually mate and produce fertile offspring
Morphological Concept of species
Defining a species as a group with similar morphology (structure)
eg. Humans
> Homo Sapiens and Homo Neanderthelensis
Phylogenic Concept of species
Based on evolutionary history
Species defined by smallest clade that can trace its evolutionary origins to a common ancestor
More important than biological concept, as Phylogenic can be applied to asexual organisms and even bacteria
Interspecific Hybrids
Combination of two different parent species
Hybrids often become infertile
eg. Mule
- Because horses have 64 chromosomes and donkeys have 62
- Mule inherits 63 total chromosomes, leaving one chromosome without a pair - meiosis cannot occur
Fertile hybrids
Some species who mate with closely related species are able to produce fertiel offsprings
eg. Ligers
- Female ligers are fertile, males are not
Alopatric Speciation
One species may diverge, giving rise to two new species, when:
- Parent population divided by geographical barrier
- No gene flow between daughter population
- Mutations arise in each population
- Different selection pressures operate in each population
Eventually daughter populations become so different that they can no longer mate and produce fertile offsprings with each other
Adaptive Radiation
Rapid speciation of one species into many, filling different ecological niches
eg. Galapagos Finches
- evolved to adapt to different sources of food
Sympatric Speciation
Speciation with strong gene flow
Evolution of a new species from a surviving ancestral species, while both continue to inhabit same geographical region
Sympatric speciation uncommon in animals, though very common in plants, as they are polyploidy
- Sympatric Speciation is thought to occur in animals due to disruptive selection
Polyploidy
Possessing more than 2 sets of chromosomes
Disruptive selection
Selects against average individual in population
Mould Fossils
fossil formed when a living thing decomposes underneath sediment, creating a cavity in the shape of the dead organism
Cast Fossil
fossil formed when a
mould fossil is filled with sediment
Petrified Fossil
impression fossils, but the organism does not decay, it is simply replaced with minerals over time.
Trace Fossil
Geological records of activity (footprints, scats)
Conditions for Fossilization (x4)
- left intact
- rapidly buried, preferrably underwater
- decompose slowly due to lack of oxygen
- consisting at least partly of hard parts
Fossil Record provides evidence that:
- Life in past was relatively simple
- Many species that used to exist are now extinct
- Many existing species did not live in the past
- Where species lived and why
- Some species that existed where transitional between ancestral and modern species
Transitional Fossils
Both primitive and derived traits - providing evidence ancestral species evolved to become more modern
Primitive Trait
Traits possessed by earlier, ancestral species
Derived Trait
Trait unique to descendant species
Punctuated Equilibrium Theory
Proposed that after a period of rapid evolution following a speciation event, species will become stable for long time
Quick bursts rather than gradual
Strategraphic Correlation
Involves Matching layers of rock in one location with rock layers in another
Often done using index fossils
Index fossils
Fossil useful for dating and correlating strata in which it was found
- Fossils dated using radiometric methods - found near volcanic rock
- When some fossils are found in other sedimentary layers, they can be used to date those layers
- Relatively short lived
Conditions for index fossil: (x4)
- Distinctive
- Abundant
- Distributed World Wide
- Have existed for only a short period of time
Big Picture Order
Taxonomic hierarchy system to classify organisms
Steps of Fossilization (x4)
Step 1
Organism dies underwater
Step 2
Layers of sediment accumulate on top of dead organisms
Step 3
Hard parts of organism impregnate with minerals
Step 4
Uplift and Erosion
Preserved Remains
Organisms preserved in amber, ice or tar
Carbon Film
Formed when liquids or gases leave a ‘picture’ on a surface
Homologous Structures
Structure with same ‘plan’ but different purpose
Evidence of evolution from homologous structures
Bats have wings, but same arrangement of bones as human hand
Suggests bats have evolved from ancestor wwith 4 fingers and thumb
Mammals, birds, reptiles and amphibians have the same arrangement of forelimb bones
Yet they serve difference functions within different organisms
Homology suggests modifications to basic plan of common ancestor’s forelimbs
Evidence of Evolution from Vestigial Structures
In many cases. vestigial structures have been reduced in size, and are only partially formal
Existence is enough evidence to prove species descended from ancestor that required that feature
eg. Diminitive wings of emus, or kiwis
Vestigial Structure
Anatomical feature that no longer surves the purpose in current form of species, but did in ancestor
Evidence of Evolution from Comparative DNA Sequences
Species more closely related are more biochemically similar
Species that have diverged from common ancestor more recently have fewer base differences in there DNA, as they have had less time for mutations to accumulate in their genome than species sharing ancient ancestor
Measured through:
> DNA Sequencing
> DNA-DNA Hybrization
DNA Hybridization
Method of comparing degree of similarity between DNA from two species, by joining, and testing how tightly joined they are
DNA Hybridization Steps (WILL IT BE ON SAC?)
Dideoxynucleotide
nucleotide missing an oxygen on the third carbon, prevents other nucleotides being added
DNA Sequencing
Evidence of Evolution from Comparative Amino Acid Sequences
Possible to determine relatedness of species based on similarity of amino acid sequences in proteins
There are fewer differences in Amino Acid sequences, as DNA mutations do not effect amino acid sequences
For this reason, proteins are often used to compare relatedness of more distantly related species
Most useful proteins to compare are those shared by all living things
Relative Dating
A comparison of age
Relative dating arranges geological events in a sequence
Seen as valuable evidence in support of speciation
- Ancestrall species appear to be responsible for appearance of subsequent species
Does not give indication of exact age of fossils, but rather whether a fossil is older or younger than another
Law of Succession
that fossils of the same age will be in the same layer of sedimentary rock
and fossils found in a higher or lower sedimentary layer will be younger or older, respectively.
Stratigraphy
branch of geology concerned with the order and relative position of rock layers and their relationship to the geological timescale
Law of Superposition
‘in an undisturbed sequence of rocks, the oldest layer lies at the bottom and successive higher layers are younger’
Transitional Fossils
Show traits between ancestral group and its descendants
Absolute Dating
Method used to determine age of rock layers, fossils or geological events as accurately as possible
Atoms have isotopes, which break down over time and go through radioactive decay
After every half life, 50% of parent element decays into daughter element
Radiometric Dating
method of absolute dating that uses minerals in rocks as geological clocks
Radioactive Decay
Half the time (half life) taken for mineral to radioactively decay
Radioactive Isotopes (x4)
- Carbon-14
- Uranium-235
- Potassium-40
- Rubidium-87
Carbon-14
Daughter Product: Nitrogen-14
Half Life: 5730 years
- Used for dating organic remains
- Useful up to 60,000 years
Uranium-235
Daughter Product: Lead-207
Half Life: 710,000,000 years
- Used for dating igneous rocks containing uranium based material
- Useful for 10,000,000 years and older
Potassium-40
Daughter Product: Argon-40
Half Life: 1,300,000,000 Years
- Used for dating igneous rocks containing k-bearing minerals
- Useful 500,000 years and older
Rubidium-87
Daughter Product: Strontium-87
Half Life: 47,000,000,000 years
- Used to date most ancient igneous rocks
Taxonomy
Classification and naming of organisms
Linneaus’ Hierarchal Classification System
Classification based on physicality, such as fur, or teeth, rather than behaviour, such as flying
Related
Sharing a recent common ancestor - relative to the context of discussion
Phylogeny
Evolutionary history of species or group of species
- We can estimate how long since two species shared a common ancestor by comparing DNA
> Sequencing Genome
> DNA-DNA hybridization
Taxonomy based on genetic similarity
Modern taxonomy is based on evolutionary relatedness
Based on how long since they shared a common ancestor
Taxonomy based on Evolutionary Relatedness
In most cases, classification based on phylogenetics will align with classification based on physical features
Phylogenic trees
Diagram showing evolutionary relationships between species
Further to the left = further back in time to find common ancestor
Scaled Branches
Indicate amount of time involved in evolution
Phylogram
Phylogenic tree with scaled branches
Cladograms
Phylogenic trees without scaled branches; showiung relationship, but not time between groups
Root
The original species, that others evolved from
Node
Splitting point, where on species turns to two
Branch
An ‘edge’ between nodes
Leaf
End node, where the species is shown
Sister Texta
Two closely related species
Homoplasy
Feature found in two, unrelated species, having evolved independantly, due to the same selection pressures
Polyphly
Group of simialr organisms without common ancestor
Convergent Evolution
Wombats and Groundhogs share many similar features, but are not closely related at all
Because they occupy a similar niche, natural selection has favoured similar adaptations
Adaptive Potential
ability to overcome a threat
Antigenic Drift
Minor genetic changes over time in an antigen
- this makes curing disease hard, as disease may change over time
Analogous Structure
features of different species that are similar in function but not necessarily in structure
- do not derive from a common ancestral feature
6 Types of Fossils
- Mould Fossil
- Cast Fossil
- Petrified Fossil
- Carbon Film
- Trace Fossil
- Preserved Remains
Clade
a group of organisms believed to comprise all the evolutionary descendants of a common ancestor.
