Classification and Evolution Flashcards
Define classification
- Placing living organisms into groups
- Based on similarities and differences
How are species classified?
- Morphology (observable features)
- Biochemistry e.g. cytochrome C
- Genes
- Shared evolutionary past (phylogeny) - determined through genetic analysis and fossil record
What is a hierarchy of taxa?
- When species are classified into a series of taxa
- Each taxa contains a larger range of organisms than the one before
List the hierarchy of taxa
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Did King Philip Came Over For Good Soup
What is the mnemonic for hierarchy of taxa?
Did King Philip Come Over For Good Soup
What are the 3 domains?
Archaea, Eubacteria, Eukaryote
What are the 5 kingdoms?
Prokaryotae, Protocista, Fungi, Plantae, Animalia
Explain why viruses are not assigned to any domains
Viruses are not considered to be living organisms
Explain why viruses can be considered to be non-living
- No metabolism
- Cannot reproduce by themselves - need a host cell
What is the binomial system?
System used to name species
How is the binomial system used?
Genus species
How and why have classification systems changed over time?
- Living organisms classified based on major differences in characteristics.
- Scientific advances allowed smaller details to be observed.
- Further advances allowed DNA and proteins to be studied - provided evidence for evolutionary relationships
Explain why prokaryotes are now classified as two separate domains
Advances in biological techniques found
- rRNA differs
- Cell walls differ (peptidoglycan not found in archaea)
Define species
Group of organisms that can reproduce with one another and produce fertile offspring
What is the purpose of using classification systems?
- Allows easier identification of a species
- Can help identify common ancestors
- It is universal so avoids problems of local names of organisms
What could cause a species to be reclassified?
New evidence showing that a previous taxon contains species that have evolved from different ancestral species
Give the molecule evidence that can be used to identify organisms as belonging to a different species
- Genetics (DNA)
- RNA
- Cytochrome C (protein found in living organisms)
How is it possible to confirm over a long period of time if organisms belong to the same species?
- Interbreed organisms
- Determine if offspring are fertile
- If offspring are infertile then different species
What is the function of a dichotomous key?
- Used to identify plant and animal species
- Based on their charachteristics
Define phylogeny
Phylogeny is the evolutionary relationships between organisms
Explain how phylogeny is related to classification
- Phylogeny is the basis of scientific classification
- The closer the evolutionary relationship, the closer the taxonomic grouping
Define phylogenic tree
- Tree diagrams that show the most probable sequence of evolutionary divergence
- A branch ‘node’ contains organisms that are related and must share common ancestry
How can phylogenic trees be used to discover evolutionary relationships?
- Used to find out how closely related organisms are
- Used to find the probable sequence in which the groups split
- A % difference in amino acid sequence used to estimate a time scale
How does phylogenic approach differ from biological species concept?
- No need to test for interbreeding (to see if offspring fertile)
- Seeks to determine common ancestor
- Can apply to organisms that reproduce asexually
- Can apply to extinct organisms
What is the advantage of phylogenic classification?
- Takes into account evolutionary relationships that are not obvious from characteristics
What is the biological definition of the term evolution?
The cumulative change in the heritable characteristics of a population
Define the theory of evolution
- Many species extinct/alive came from simple life forms which first developed more than 3 billion years ago
Which two scientists first published the theory of evolution?
Darwin and Wallace
Describe the work of Lyell, Darwin and Wallace
- Lyell - suggested fossils were evidence of animals that lived millions of years ago
- Darwin - came up with theory of evolution by studying finches in Galápagos islands
- Wallace - came up with theory of evolution by natural selection in Borneo
Summarise Charles Darwin’s finding on the HMS Beagle
- Visited Galápagos islands
- Large seeds require large beak finches
- Small seeds require small beak finches
- Medium beak finches feed on a variety of size seeds
- Beak size = heritable characteristic
- Climate on Galapagos varied a lot - in droughts only larger seeds survive
- Darwin found a significant drop in small beak finches after drought
Explain how evolution may happen in response to an environmental change
- Variation in population due to mutation
- More offspring are produced than can survive
- Struggle for survival / survival of fittest
- Those with most favourable alleles more likely to survive and reproduce
- Favourable alleles passed on to offspring
- Frequency of favourable alleles increases in population over many generations
- This is evolution by natural selection
Outline the types of evidence that can be used to support the theory of evolution
Fossils
- Show species changed over time
Comparative biochemistry
- Show common ancestry and when species diverged
Comparative anatomy (homologous structures)
- e.g. pentadactyl limb
- Show common ancestry
Why is natural selection now more widely accepted by scientists than it was in the 19th Century?
- Fits current evidence
- More evidence since nineteenth century
- Development of scientific techniques (e.g. DNA sequencing)
Define fossil
Remains of plants and animals found in rocks
How are fossils formed?
Hard parts of plants and animals which do not decay
- Conditions for decay are absent e.g. low temperatures, no oxygen
- Preserved traces e.g. plant rootlets, footprints
Why is the fossil record incomplete?
Many organisms are soft bodied
- Decompose before they can fossilise
- Conditions for fossilisation often not present
- Many fossils destroyed by natural processes or not yet discovered
Outline how fossil records can provide evidence for evolution
- Fossils show changes over time
- Fossils can be dated e.g. with radioisotopes
- Simplest / most different from modern species found in oldest rocks
- Shows relationships between species
- Many fossilised organisms no longer exist
- DNA extracted from some fossils can be compared with living organisms
Explain how comparative biochemistry provides evidence of evolution
Study of similarities and differences in proteins and DNA of an organism
- Changes in molecules can help identify evolutionary links
- e.g. cytochrome c, ribosomal RNA
- Species that are closely related have the most similar DNA and proteins
Define homologous structures
Structures which have evolved from the same part of a common ancestor
- e.g. pentadactyl limb
Describe how the pentadactyl limb can be used as evidence for evolution
4 groups of vertebrates have pentadactyl limb: amphibians, mammals, reptiles and birds
- Pentadactyl limb has multiple functions
- All groups have a common ancestor
- Through evolution the limb became adapted to suit different uses - adaptive radiation
Define divergent evolution
Different species have evolved from a common ancestor
- Each with a different set of adaptive features
Outline the process of adaptive radiation
Ancestral species occupies new environment
- Different members of the species exposed to different selection pressures
- Gives rise to new species that share common structures adapted to new environment
- e.g. pentadactyl limb, Galapagos finch beaks
Define variation
Differences between organisms
Define interspecific variation
Variation between members of different species e.g. numbers of legs
Define intraspecific variation
Variation within a species e.g. hair colour
Give the factors that cause variation
Genetic variation - differences in the genetic material inherited
Environmental variation
List the causes of genetic variation
- Different alleles
- Mutation
- Meiosis
- Sexual reproduction
- Chance
How can different alleles lead to genetic variation?
Genes have different alleles - individuals in a species population may inherit
different alleles of a gene
How can meiosis lead to genetic variation?
Crossing over of non-sister chromatids leads to mixing of genetic information
- Independent assortment leads to gametes of an individual showing variation
Give an example of a characteristic that shows both environmental and genetic causes
- Skin colour
- Height
Explain why genetic variation is more common in organisms that reproduce sexually
- DNA can only be altered by mutation
- Individuals produced by asexual reproduction are clones
- Meiosis does not take place
What two types of characteristics caused by variation exist?
Discontinuous and continuous
Define discontinuous variation
Usually affected by genes alone (not the environment)
- e.g. blood groups are A, AB, B, O
It can only take particular values
Categoric
Define continuous variation
May be affected by both genes and the environment
- e.g. height and weight
Can take range of values
Not categoric
State the pattern of inheritance that contributes to continuous variation
Polygeny (more than one gene)
Define polygenic inheritance
Continuous variation which depends on the effect of more than two genes
Explain how polygenic inheritance gives rise to continuous variation
Example: Human skin colour
- Can vary from pale to very dark
- Skin colour controlled by alleles from several genes
- No alleles are dominant (alleles are co-dominant)
- Many different possible combinations of alleles
- Skin colour controlled by combination of alleles
When plotted onto a graph, what shape does continuous data usually produce?
Normal distribution curve (bell-shaped)
What is standard deviation a measure of?
How spread out data is
The greater the SD, the greater the spread
What does a large SD tell you about the the variation in a population?
Large SD = large amount of variation
Define adaptation
Characteristics that increase an organism’s chance of survival
List three types of adaptations
Anatomical
- Physical features
Behavioral
- The way an organism acts
Physiological
- Process that takes place inside an organism
Examples of anatomical adaptations
Camouflage - allows organism to blend in
Teeth - sharp teeth kill prey and tear meat
Define innate behaviour
Ability inherited through genes e.g. spider spinning web
Define learned behaviour
Learnt from experience and observing others e.g. using tools
Give examples of behavioral adaptations
Survival behaviors e.g. playing dead
Migration
Courtship e.g. feather display
Examples of physiological adaptations
Poison production
Water holding e.g. cactus
Define analogous structures
Features that have adapted to perform same function
Have different genetic origin e.g. tall fins of whales and fishes
State the difference between analogous and homologous structures
Analogous structures - have adapted to perform same function but have different origin
Homologous structures - appear superficially different but have same underlying structure
Define convergent evolution
- When unrelated species share similar traits
- Occurs when organisms adapt and evolve to similar environments or selection pressures
How do marsupial moles and placental moles provide evidence for convergent evolution?
They have analogous structures
- Both burrow through soft soil to find insects, both have velvety fur for smooth movement through soil
Define selection pressures
Factors that affect an organism’s chance of survival or reproductive success
Outline the process of natural selection
- Variation due to mutation
- Change in selection pressures
- Those with most favourable alleles more likely to survive and reproduce.
- Less well adapted organisms die or fail to reproduce
- Advantageous alleles passed to offspring
- Frequency of favourable alleles increases over generations
- Can eventually lead to evolution of a new species
Prokaryotae features
- Unicellular
- Peptidoglycan cell wall
- No nucleus or membrane-bound organelles
