5.1, 5.2, 5.4,10.3 Evolution, Natural Selection, Clasistics, Gene Pool speciation Flashcards
Heritable
One generation to the next through genes
Cumutive
One change is usually not enough to have a major impact on the species
More and more have to be effected over time
Population
Change cannot affect only 1 individual
Evolution
The process of cumulative change in the heritable characteristics of a population
How do fossils form?
.1. Death
- Scavengers feed on fleshy body leaving skeleton/ shell
.2. Deposition
- Skeleton/ shell slowly becomes covered with dirt, sand/ silt
- Thousands of years pass
.3. Permineralization
- Chemicals in shell/ skeleton undergo chemical changes
- Chemicals are replaced w rock-like minerals
.4. Erosion
- Movement of earth plates move rock and fossil to surface
.5. Exposure
- Natural erosion exposes the fossil
Fossil Record
- Evidence that species evolve over time based on dating rock
- The fossil record provides evidence by revealing the features of an ancestor for comparison against living descendants
Evidence of evolution
3
Selective Breeding:
- A form of artificial selection, whereby man intervenes in the breeding of species to produce desired traits in offspring
- Dog breeds, chicken breeds for egg/ meat
Fossil Record:
- Evidence that species evolve over time based on dating rock
Homologous Structures
- Araise from sharing a common whereby several new species rapidly diversify from an ancestral source
- Homologous structures illustrate adaptive radiation
- 3 examples
Homologous Structures Examples
Comparison of the pentadactyl limb of mammals
- Mammals, birds, amphibians and reptiles all share a similar arrangement of bones in their appendages based on a five-digit limb
- Use of locomotion (forms of getting around) to compare species
Plasma Membrane
- Structure of plasma membrane in eukaryotic and prokaryotic structures are similar
- All consist of phospholipids
Universal Genetic code
- The standard genetic code
- AUG, GCA etc.
Charles Darwin
- Discovered organisms elolve over time due to natural selection’
- Daphne Major beaks were different and evolved to suit their diet
Peppered moth example
- During the industrial revolution, trees were covered in sut causing industrial melamism in over 70 species of moths.
- Natural selection –> The moths melanin increased to change the colour from white to brown so they could camouflage on the darker trees
= For vs against in different environments
Natural Selection
- The mechanism for evolution –> elolution occurs bc of it.
- Can only occur if there is variation amoung members of the same species (for vs against certain traits)
- Mutation, meiosis and sexual reproduction in organisms that reproduce causes variation in species due to heritable traits
Adaptations
- Adaptations are features of organisms that aid their survival by allowing them to be better suited to their environment
Can be:
Structural: Physical differences in biological structure
Behavioural: Differences in patterns of activity
Physiological: Variations in detection and response by vital organs
Biochemical: Differences in molecular composition of cells and enzyme functions
Developmental: Variable changes that occur across the life span of an organism
Darwins theory
Variation exists amoung individuals within species
Variations arise from:
- Mutation
- Crossing over during prophase 1
- Random assortment of chromosomes during metaphase one
- Sexual reproduction
Organisms have more offspring than the environment can handle
Competition amoung individuals
- Intraspecies = Same
- Interspecies = Different
Best fitted variations that fit to environment are likely to survive and reproduce and pass on characteristics to next generation
Gene Pool
A gene pool consists of all the genes and their different alleles, present in an interbreeding population.
- Sum of all the alleles
Evolution and alleles
Evolution requires that allele frequencies change with time in populations.
Changes to allele frequency within a gene pool (evolution) can result from five key processes
Reproductive isolation
Can be temporal, behavioural, or geographic
Reproductive isolation due to behaviour
- When two populations exhibit different specific courtship patterns
- Species used to be the same, but natural selection differenciates them due to bahaviours.
Temporal Reproductive Isolation
When two populations differ in their periods of activity or reproductive cycles
Geographic Reproductive Isolation
when two populations occupy different habitats or separate niches within a common region
- Change due to diversing in geographic location
Speciation
When populations gradually diverge into seperate species by evolution
Pace of elolutionary change
Punctual = missing intermediate fossils in the fossil record
- species remain stable for long periods before undergoing abrupt and rapid change
- Sudden changes in environment (industrial revolution)
Gradual = Steady change
- speciation generally occurs uniformly, via the steady and gradual transformation of whole lineages
Genetic drift
The change in the composition of a gene pool as a result of change or random events
Bottle neck:
- when an event reduces population size by over 50%
Flounder effect:
- small group breaks away from the population to establish themselves in a new territory
Allele frequences
- represent the prevalence of a particular allele in a population, as a proportion of all the alleles for that gene
- represented as a percentage or 0.0 - 1.0
Stabilising Selection
- Where an intermediate phenotype is favoured at the expense of both phenotypic extremes
- Results in removal of extreme phenotypes
Directional Selection
- Where one phenotypic extreme is forced to change due to the environment
- This causes the phenotypic distribution to clearly shift in one direction
Disruptive selection
- Where both phenotypic extremes are favoured at the expense of the intermediate phenotypic ranges
- This causes the phenotypic distribution to deviate from the centre and results in a bimodal spread
Polyploid
- Organism w/ more than 2 sets of homol. chromosomes.
- Resulting from hybridization between different species or from the same ancestral species when chromosomes duplicate in preparation for meiosis but then meiosis doesn’t occur
Clades
A group of organisms that have evolved from a common ancestor
Analoguous and Homologuous
Homologous
- Similar because of similar ancestry (ex. Pentadactyl limbs)
Analogous
- Similar because of convergent evolution
- (human & octopus eye – function the same, but evolved independently)
Cladograms
Are tree diagrams that show the most probable sequence of divergence in clades
Show evolutionary relationships and demonstrate how recently two groups shared a common ancestry
Could be data base questions
Reclassification of the figwort family using evidence from cladistics
- DNA evidence identified different common ancestors
- Analoguous (convergent evolution)
