Evolution Flashcards
What is the theory of evolution?
Proposes that all organisms have developed from previous organisms, all life can be traced back to one common ancestor
What is evolution?
Process of cumulative, heritable changes in a population over many generations
What is an ancestor?
A species from which another species has evolved from
What is a common ancestor?
An ancestor shared by different species where there is common genetic code
What are 4 things that are evidence for evolution?
- Fossil record
- Comparative anatomy
- Comparative genomics
- Comparative Biochemistry
What are fossils?
Preserved remains or traces of an organism, only portions of the deceased organism (bones, teeth)
Name and explain the 4 processes of fossilisation.
- Death and decay
- Organism dies and soft body parts are decomposed or scavenged leaving bones - Deposition
- Remains are covered rapidly with silt and sand, over time more layers continue to build - Mineralisation
- Pressure from the covering layers causes hard organic materials to be replaced by minerals - Erosion/Exposure
- Movement of tectonic plates may displace fossil and return it to the surface for discovery
What are 3 alternative ways a fossil can be preserved other than the original fossilisation method?
- Freezing and dehydration
- Soft material (eg. ash) falling on impressions
- Impressions made in sandstone and mudstone
What are 4 conditions for fossilisation to occur?
- Hard body parts are needed, soft body parts don’t usually fossilise
- Preservation of remains, protection from scavengers and environmental damage
- High-pressure levels to promote mineralisation
- Anoxic (low oxygen) to protect against oxygen damage and decomposition
What are 3 biases of fossilisation?
- Fossilisation is rare and very few organisms are preserved
- Favors organisms with hard body parts
- Favors organisms that were widespread and existed for a long period before going extinct
What 3 key things does the fossil record show?
- Organisms in the past are not the same as organisms alive today. (eg phylogeny of a horse)
- Organisms have become more complex over time. (eg protists -> invertebrates -> vertebrates)
- Shows there are common ancestors, but may have missing links
What are transitional fossils? Give an example.
- Fossils that fill the gaps between ancestor and descendant as they show traits from both ancestor and descendant.
- Strongly suggestive of evolution as they show the progression form.
- eg Archaeopteryx. Shows the dinosaur-to-bird transitional form
What is superposition?
Suggests that older lock layers are deeper while new layers are closer to the surface
Name and describe 2 methods for dating fossils.
- Comparative dating: How old the rock containing the fossil is compared to the surrounding rock
- Absolute dating: Involves the use of techniques that can assign a numerical age to a fossil
What are 3 techniques used for absolute dating?
- Radiometric dating: measured with known rates of atomic decay eg. carbon dating
- Electron spin resonance: Trapped electrons gain magnetic force to environmental radiation over time
- Luminescence techniques: Measure light emitted from a material
What is comparative anatomy?
The study of similarities and differences in the anatomy of different species
What are 3 types of comparative anatomy?
- Homologous structures
- Embryology
- Vestigial structures
What are homologous structures?
Similar structures in different species have evolved from a common ancestor to serve different functions.
What is embryology?
Study of the formation and development of an embryo and phetus
What are 3 things comparing embryonic development shows?
- All terrestrial animals have non-functioning gill slits as early embryos suggesting an aquatic origin
- Many vertebrates have a primitive tail in embryonic development
- Closely related species go through similar stages of development
What do similarities in embryonic development suggest?
Organisms share a common evolutionary pathway
What are vestigial structures?
Structures in organisms that have lost most if not all function in the course of evolution
What is a pentadactyl limb?
A hand or foot with 5 fingers or toes, has been modified for a wide variety of functions
What do homologous structures suggest?
Common ancestory
What is the evolutionary explanation of the pentadactyl limb?
All 4 footed animals have descended from a common ancestor that had a pentadactyl limb, easier to evolve variations of the limb than to recompose whole limb structure
What are 4 examples of vestigial structures in humans?
- Appendix
- Gall bladder
- Wisdom teeth
- Male breast tissue & nipples
What are analogous structures? Give an example.
Features of organisms that have a different structure for the same function. eg Shark fins vs penguin fins
What is divergent evolution? Give an example.
When related species evolve traits over time away from the common ancestor to create new species. eg common ancestor evolving into lion, puma, cat, leopard
What is convergent evolution? Give an example.
When unrelated species evolve similar adaptations to their environments. eg pangolins and numbats, same elongated snout but very distantly related
What is genomics?
Study of genes and the interactions within a genome
What is comparative genomics?
Using genetic tools to research and compare the genome sequences of different species. The more similar the sequence, the more closely related the species
What 2 molecular methods can be used in comparitive genomics?
- DNA sequencing
- DNA hybridisation
What is DNA hybridisation?
- Comparing 2 different strands of DNA by denaturing the strands and annealing 2 different strands together, then denaturing to see how similar the DNA of different organisms are.
- If hybridised DNA requires a higher temp to denature, organisms are more closely related
What can scientists do using comparitive genomics?
- Measure the difference between organisms
- Trace evolutionary relationships
- Construct phylogenic trees
What is comparitive biochemistry?
Comparing similarities and differences of amino acid sequences and the proteins produced in different organisms
Provide an example of evidence for evolution using comparitive biochemistry.
Amino acid chains of common proteins such as haemoglobin found in many organisms are analysed and the similarities and differences in the amino acids provide evidence for evolution
Besides evolution, what else can comparitive biochemistry show and how?
Shows the relatedness of organisms, determined by the number of differences in ammino acid sequences
What are gene pools?
Sum of all alleles within a population
What are the 4 mechanisms of evolution?
- Mutation
- Natural selection
- Genetic drift
- Gene flow
What is genetic drift?
Random non-directional change in allele frequencies caused by chance, not selection pressures
What is gene flow?
Transfer of alleles as a result of migration of individuals from one population to another, due to immigration and emigration of individuals
What is the bottleneck effect?
Extreme example of genetic drift,w occurs when a population size is drastically reduced (after natural disasters), gene pool of new population is not representative of the original
What is the founder effect?
Extreme example of genetic drift, occurs when a small group of individuals leave their original population and start a new one in a different location, alleles in new population will be different to original population
What are 3 main effects of genetic drift?
- Traits being under or over-represented in new population
- Traits being lost completely from the gene pool
- Unusual traits being preserved (allele fixation)
What is natural selection?
A process where individuals with advantageous inheritable traits survive and reproduce more successfully than other individuals leading to evolutionary change in a population
What are the 6 key principles of natural selection?
- Variation
- Over-production
- Survival of the fittest (competition)
- Higher reproductive rate
- Heritability
- Allele frequencies change
Explain the 1st key principle of natural selection
Variation
- Individuals in a population will genetically vary in size, colour, ability to avoid predators, ability to resist disease etc.
-Explains why some individuals survive in a changing environment
Explain the 2nd key principle of natural selection
Over-production
- Most species produce more offspring than the environment can support
- Not all offspring will survive to reproduce
Explain the 3rd key principle of natural selection
Survival of the fittest (competition)
- Resources can be limited, competition arises and only the strongest and best-suited individuals with favourable characteristics survive to reproduce
Explain the 4th key principle of natural selection
Higher reproductive rate
- Individuals that have the desired trait survive to reproduce, having a higher reproductive rate then those without the allele
Explain the 5th key principle of natural selection
Heritability
- Higher reproductive rate means the desired trait is more likely to be passed on to the offspring
Explain the 6th key principle of natural selection
Allele frequency changes
- As traits are now inherited, frequencies change in the population as the cycle continues over generations, increasing the frequency of favourable features
What are adaptations?
Features of an organism that aid their survival by allowing them to be better suited to their environment
Give an example of adaptation
Peppered moth
- Originally a dark colour, adapted to a lighter peppered colour to camouflage with trees
What are 5 types of adaptations? Give examples
- Structural: Physical differences in structure. eg giraffe neck length
- Behavioural: Differences in patterns of activity. eg possums faking death when threatened
- Physiological: Variation in detection and response by organs eg. colour perception
- Biochemical: Differences in molecular composition, cells and enzyme function eg. blood groups
- Developmental: Variable changes that occur across the lifespan of the organism eg. aging patterns
Apply 3 types of adaptions to an echidna
Structural: Sharp quills for protection, long snout for eating
Behavioural: Curls into a ball when scared, digs burrows as shelter
Physiological: Sensitive ears to hear ants, tounge can stiffen and penetrate soil (change in blood flow)
What is accumulation?
Process of particular traits becoming more common over generations
Explain selection pressures
- External agents that affect an organism’s ability to survive
- Can be positive or negative selection pressures
- May not remain consistent, alters what could be a beneficial trait
What are 3 types of selection pressures?
- Resource availability: Presence of food, shelter, mates
- Environmental conditions: Temp, weather, geographical conditions
- Biological factors: Predators, pathogens
Density-dependent selection pressures
- Predators
- Availability of resources
- Nutrient supply
- Disease
- Accumulation of wastes
Density-independent selection pressures
- Phenomena (natural disasters)
- Abiotic factors (temp, CO2 levels)
- Weather conditions (rainfall, storms)
What is adaptive radiation?
A process where an organism rapidly diversifies into many different forms with different adaption. eg galapogous island finches
Give 3 examples of environmental influence on variation
- Flamingos: not born pink, accumulation of red pigment from shellfish
- Hydrangeas: Acidic soil makes blue flowers, basic soil produces pink flowers
- Siamese cats: Fur colour is influenced by temperature, low temp on body extremities causes pigment production
What is micro-evolution?
- Change in frequency of alleles in a population
- Changes in gene pool over a relatively short period of time
What is macro-evolution
- The process of the evolution of new groups of organisms, consisting of many related species. Occurs through multiple speciation events
- Major evolutionary changes above the species level of classification
What is the process of macro-evolution?
- Natural selection favours desirable traits, changing populations over time as gene pools accumulate the small changes (micro-evolution)
- Eventually a population accumulates enough changes that speciation occurs and a new species can be identified
- Rapid speciation events lead to collection of new species or higher classification
What are the 5 phases of speciation?
- Variation
- Isolation
- Selection
- High survivability and reproduction
- Speciation
Explain the 1st step of speciation
Variation:
- One population, one species
- Variety of characteristics within the population
- Population shares common gene pool
Explain the 2nd step of speciation
Isolation:
- 2 populations, 1 species
- Barrier forms which prevent the 2 populations interbreeding
- 2 separate gene pools
Explain the 3rd step of speciation
Selection:
- 2 populations, 2 subspecies (1 species)
- Over generations selection pressures change gene frequencies in both gene pools
Explain the 4th step of speciation
High survivability & reproduction
- 2 populations, 2 subspecies (1 species)
- Only some organisms with favourable genes survive and reproduce, passing on the trait
- Gene frequencies increase for that trait
Explain the last step of speciation
Speciation:
- 2 populations, 2 species
- Isolation and selection continue, and gene differences become so large populations can no longer interbreed meaning they are 2 separate species
What are the 2 types of speciation?
- Allopatric speciation: Geographical barrier physically isolates populations preventing reproduction
- Sympatric speciation: Reproductive isolation as a result of genetic abnormality, no physical barrier
What are 2 mechanisms of speciation?
- Pre-reproductive
- Post-reproductive
What are 4 types of pre-reproductive speciation mechanisms
- Geographical features (allopatric)
- Temporal mechanisms eg. different breeding seasons (sympatric)
- Behavioural mechanisms eg. different mating calls (sympatric)
- Morphological mechanisms eg. different reproductive structres (sympatric)
What are 3 types of post-reproductive speciation mechanisms
- Gamete mortality: gametes don’t survive after mating (sympatric)
- Zygote mortality: zygote forms but doesn’t survive (sympatric)
- Hybrid sterility: offspring develop but cant reproduce (sympatric)
What are mass extinctions?
Occur rarely, periods with a high rate of extinction
3 key points about mass extinction
- Can be natural or human causes
- Large populations can be more resilient than small ones
- Reduced genetic diversity due to bottle necks
What is conservation?
Aims to maintain viable gene pools with consideration of biogeography, reproductive behaviours and population dynamics
What are 4 practices of conservation? Explain them.
- Reserves: large protected areas
- Wildlife corridors: areas of large space allowing organisms to migrate when resources are scarce
- Transgenic organisms: Designed to resist diseases and extinction
- Biotechnology: monitoring endangered species, assessing gene pools
