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Evolution and biodiversity (V) - Coggle Diagram
Evolution and biodiversity (V)
Evidence for evolution
Homologous structures
May look superficially different and have different functions,
but actually evolved from the same origin (mammalian forelimbs)
They have a unity of type
They became different because they perform different functions
Adaptive radiation
Analogous structures
Similar structures with different origin (fish and wale fins)
They became similar only because they
perform the same function
Convergent evolution
Both structures are difficult to explain without evolution
Selective breeding
Artificial selection
Modern breeds are very different from wild species
It shows that selection can cause evolution
Speciation & patterns of variation
The populations will evolve in different ways
If they are not able to interbreed anymore, new species are created
If two populations of same species separate (they don't interbreed), natural selection will act differently on each
The continuous range in variation between populations provides evidence for the evolution of species
Types & causes
Sympatric (behavioural separation): differences in their behaviours, e.g. mating rituals
Sympatric (temporal separation): mating at different times of days/seasons
Allopatric (geographical separation)
Punctuated patterns: sudden changed followed by stability
Gradual patterns: long sequence of continuous intermediate forms
Fossils
The sequence fits in with the ecology of the group
Many sequences are known: finding common ancestors
The sequence in which fossils are found matches the one that they were expected to evolve into
Dating of geological eras allows to tell the age of fossils
Natural selection
Offsprings
This causes a struggle for survival and a competition for resources
The best adapted individuals will produce many offsprings
Generally, species tend to produce more offsprings than the environment can support
The less well adapted individuals will stop reproduction and die
Adaptation
They don't develop during the lifetime of an individual, takes more generations
Acquired characteristics (lifetime) cannot be inherited
Adaptations develop from natural selection not with the direct purpose of suit the individual to its environment
There is an increase in the proportion of individuals in a population with characteristics that make them well adapted
Variations
Meiosis (crossing over & random orientation of bivalents) produces new combinations of alleles
Sexual reproduction combines alleles from two individuals
Mutations causes the production of new alleles
In asexual reproduction, species only have mutations as a source of variation
Natural selection depends on variations among a population
Classification of biodiversity
Advantages
Easier identification of species
Since species in the same taxa share some ancestors, they will have similar characteristics, this allows to make previsions
Hierarchy of taxa
Four eukaryotic kingdoms: plants, animals, fungi and protista
Kingdom, phylum, class, order, family, genus, species
Three domains: Eubacteria, Archaea (prokaryotes living in extreme conditions) and Eukaryota
Species are arranged in taxa
Cladistics
A group of organisms that evolved from a common ancestor
The evidence for a species to be part of a clade comes from base sequences of genes or amino acid sequences of proteins
Morphology is now rarely used due to its unreliability (analogous and homologous traits)
Mutations (differences in DNA base sequence) occur at a roughly constant rate, so they can be used as molecular clocks
Cladograms
Two (even three or more) clades branch off at a node
The node represents a hypothetical ancestral species
Nodes are branching points on the cladogram
Benefits
Reliable because they are based on molecular analysis
Reflect how recently two groups separated
Show ancestral relationships