EVOLUTION Flashcards
what is evolution
- a general term that may be defined as a change over time that occur in chemicals, matter, solar systems and language
what is biological evolution
- can be described as a genetic changes in a population of living organisms that are inherited over successive generations due to natural selection ultimately resulting in a new species
what is macro evolution
- this is the development of new life forms or species form earlier life forms over many generations
what is micro evolution
the variations that occur within a species. small changes originate in the gene pool resulting in small changes in the genotype of the species - these changes are passs onto the the offspring
is evolution a hypothesis or a theory
- a scientific theory
what is the origin of ideas about origins
- the earth was created 4.6 billion years ago and we evolved from one common ancestor that lead to the enormous biodiversity we currently have
what are the 5 factors that are evidence of evolution
fossil records
modification
biogeography
genetics
other forms of evidence (comparative biochemistry; vestigial organs and comparative embryology)
what are homologous structures
similar structures with the same body plan that perform different functions - these then used to provide evidence of a common ancestor
what is biogeography
- the study of the distribution of existing and extinct plant and animal species in specific geographical regions.
what are the 3 major observations when studying the natural environment
- biodiversity
- organisms are well adapted
- continuous changes
erasmus darwin
his ideas
- single common ancestor
- similarities of species mean the one species developed from another
- artificial selections and metamorphosis
jean baptiste de lamarck
his theory
- the use or disuse of organs may cause organs to increase or decrease in size
- during lifetime organisms acquire certain changes in characteristics that are inherited by their offspring
alfred wallace
worked along side charles darwin to publish an article on natural selection
charles darwin
4 main observations
- individuals of population produce more offspring than required to ensure survival
- a great deal of variation occurs within a population
- some individuals are better adapted and more likely to reproduce
- characteristics are transferred from surviving parents to offspring
what is darwin’s theory of natural selection
- a large number of offspring produced
- variation in a population
- struggle for survival
- survival of the fittest
- inheritance of favourable characteristics
- change occurs over time
- new species form
what is punctuated equilibrium
- the fossil records show us fast and rapid change not gradualism like darwin suggests - either the species could not adapt and died or it did but rapidly leading to speciation
- it explains the absence of transitional fossils
what is natural selection
- survival of the fittest “nature decides”
what is artificial selection
- in the deliberate breeding of plants and animals for desired characteristics that would not necessarily benefit the survival of offspring - sheep for wool, race horses for speed etc
differences between natural and artificial selection table
N
: environment acts as selection pressure
: characteristics are advantageous for survival in natural environments
: maintains variation
A
: humans decide
: characteristics not necessarily advantageous
: decreases variation
two types of variation
continuous - a range in phenotypes from the same characteristic forms a spectrum
- a genetic characteristic may be controlled then more than 1 gene (poly genetic) and each gene may have multiple alleles - the more alleles that control a characteristic the greater the variation of possible gene combinations (eg human height)
discontinuous - phenotypes fit into separate categories eg blood type - you can only be one
What are the conditions essential for fossilisation
Rapid burial
High pressure
Low oxygen
What is divergent evolution
Where organisms develop from a common ancestor but follow different evolutionary paths
What is convergent evolution
Where organisms are not related but develop structures for similar environments completely independent of each other
What are analogous structures
Preform same function but did not originate from a common ancestor
What are analogous structures
Preform same function but did not originate from a common ancestor
What is the theory relating to the flightless birds
May have developed from a common ancestor, the birds were separated when Gondwanaland broke apart - the climate and habitat changes as a result of continental drift - the birds adapted and a new species developed due to the mutations and selections in various environments
What are 3 other forms of evidence (not the main 5)
Comparative biochemistry
Vestigial organs
Comparative embryology
What is speciation
The formation of species increases the range of organisms on earth and thus increases biodiversity
What is a species
A group of organisms that interbreed to produce fertile offspring
What is extinction
The loss of species decreases the range of organisms on earth and thus decreases biodiversity
What is a population
A group of organisms of the same species that live in a particular place and at a particular time with the ability to freely interbreed
What is a gene pool
A total number of allelles of all reproductive individuals in a particular population
What is a gene flow
The exchange of alleles between population
What is reproductive isolation
When a new species arise from an existing species, the two species can no longer interbreed: there is therefore no gene flow and they become isolated from each other in terms of reproduction
When can reproductive isolation occur
When the species is separated geographically
Or when they occupy the same area (new species arise)
What is genetic variation in a species usually caused by
Genetic recombination - meisosis( crossing over and random assortment of homologous pairs )
- reproduction (random mating and random fusion of gametes)
Mutations - gene mutations (change in base sequence - either harmful, neutral or beneficial)
- chromosome mutation (eg Down syndrome)
Mutations lead to genotypic variations in population, what are 2 examples
- finches of the Galapagos island
- white lions
What is inbreeding
Crossing of closely related individuals - usually occurs in mostly treated species where there are limited numbers of individuals or in populations with small isolated gene pools
Bc closely related individuals share more alleles it leads to a limited genotypic and phenotypic variation
Increase in homozygosity - if both recessive genes are carrying harmful mutations they will be expressed in the phenotype therefor passed to next gen
List 2 advantages and disadvantages of inbreeding
+ produces predictable offspring, recessive genes can be isolated
- high mortality rate, offspring can become sterile
What are the 2 genetic disorders that occur in humans as a result of inbreeding
Haemophilia
Tay seach’s
What is outbreeding
The crossing of unrelated individuals resulting in offspring that are genetically different-
Promotes heterozygosity where alleles differ from each other and increase genetic variation
List 2 advantages and 2 advantages of outbreeding
+Genetic variation increases, reintroduces lost charactistic
- less predictability in offspring, typical characteristics are lost
Explain the founder effect
A loss of genetic variation when a new population is formed from a small number of individuals moving to a new area - the gene pool will only contain genes from the founding members - according to evolution the isolated pop will become so different to the parent pop it can eventually form a new species
What are the 2 main types of speciation
Geographic (allopatric) speciation
Sympatric speciation
Define allopatric speciation
Is when a new species arised from an existing species when the populations are separated by a geographical barrier
These two populations are reproductively isolated and there is no gene flow
Natural selection occurs independently in each area and the two gene pools become very different in phenotype and genotype
Eventually a new species develops
Define sympatric speciation
Is when a new species arise from an existing species in the same geographical area
The new species can become isolated from the ancestoral species with respect to reproduction even if they occur in the same area
Sympatric speciation can occur as a result of polyploidy plants (multiplication in chromosome no.) and hybrid species (breeding of unrelated individuals [different species])
What are the 2 main groups of reproductive isolating mechanisms
Pre zygotic
Post zygotic
What are some examples of pre zygotic isolation
Breeding at different times of the year
Species specific courtship
Adaptations to plant to different pollinators
Physical Incompatibility in animals to prevent fertilisation
Occupying different habitats in same environment
What is an example of post zygotic isolation
Development of sterile offspring in hybrids
