5 evolution and biodiversity Flashcards
when does natural selection occur
when populations have genetic variations.Some variations are an advantage over others to the population in its particular environment. These advantages may help the organism to catch prey, avoid predators, find mates, or survive environmental changes. Those individuals that possess the most advantageous characteristics live to a reproductive age and are able to pass those characteristics to their offspring through their genes.
when does selective breeding happen
practised by humans for thousands of years, is a form of selection and another bit of evidence for evolution. In contrast to natural selection, this form is artificial and is often referred to as artificial selection. Humans select the animal or plant with the best characteristics and try, through genetic crosses, to create a breed or plant line that retains these desired characteristics. The differences between the ‘wild’ ancestor and the present day organism (created through artificial selection) can be enormous.
natural selection definition
Natural selection occurs when species have variation and certain traits are selected because they help the species to reach a reproductive age and pass on their genes.
selective breeding definition
A form of artificial selection in which organisms with certain characteristics are chosen by humans because they are of some benefit. These organisms are bred to produce offspring that have the same genes and, therefore, the same characteristics.
can artifical selection cause evolution
yes
waht is a breed
a group of animals within a species tha that haev specific and similar characteristics
microevolution
occurs on a small scale withina species
homologous
similar in position, structure, and evolutionary origin but not necessarily in function.
similarities betwen doplphins and human arms
5 phalanges
same bones (humerus, ulna, radius, carpals, phalanges)
Pentadactyl limb –
A limb with five digits, found in amphibians, reptiles, birds and mammals.
divergent evolution
when two separate species have a similar structure, but use it in different ways because of their environment.
Adaptive radiation
a process in which organisms rapidly diverge from the form of the original species into several new forms specialised to make use of different environmental niches. This can lead to divergent evolution and the development of a new species.
analogous
performing a similar function but having a different evolutionary origin, such as the wings of insects and birds.
what is convergent evolution
unrelated organisms evolve similar structures or features
waht is divergent evolution
shared ancestor but different end points (species evolve different strucutres or features)
Speciation
the process by which new species form, is one of the success stories of evolution.
discontinuous variations
not affected by environment eg blood type
is a type of variation that is influenced by a gene or a few genes, can be put into categories, and is not influenced by the environment.
continuous variations
affected by environment eg height
is a type of variation that is controlled by many genes, has a wide range of variability, and is easily influenced by the environment.
how do species form
When two species become genetically different enough that they can no longer interbreed to produce fertile offspring, then speciation has occurred. A possibility is that one species (species A) evolves over time until it is genetically different enough from the original species that it is considered a new species (species B) and so on (species C).
industrial melanism
widespread burning of fossil fuels by power machinery
The allele for the dark allele is dominant over the the light allele and codes for the moth to make more melanin, which is the pigment causing the dark colour. The darker coloured variety, also called the melanistic morph, was better camouflaged in the highly industrial areas where pollution had changed the environment. The lighter coloured moth was better adapted to non-polluted areas, because the trees were still covered in lichen and had little or no soot – making it less visible to predators. In these non-polluted areas the recessive allele for the light colour was found at higher frequency than the dominant allele for the dark colour. The result of this environmental change was that in the industrial areas the numbers of the darker moth increased, and the numbers of the lighter moth declined. This can be explained by the fact that the lighter peppered moths were easily spotted and eaten while resting on dark and sooty tree barks, while darker peppered moths were well camouflaged in polluted areas and many survived to reproduce and pass on the dark variety of the gene. Therefore, the pollution brought about by the industrial revolution caused environmental change and acted as a natural selection pressure that favoured the darker moth over the lighter moth. This led to a change in the frequency of the alleles in the peppered-moth gene-pool.
transient polymorphism
where one allele variation replaces another
balanced polymorphism
equililibrium between the two variations of the gene
Industrial melanism definiton
is the change in the melanin-producing allele frequency from light to dark due to environmental changes brought on by industry pollution.
transcient polymorphism defintiion
is the gradual change in the allele frequency of a population due to the slow replacement of one gene of another.
balanced polymorphism definition
is a balance between both forms of the allele variations within a population.
causes of variation
mutation
meiosis
sexual reproduction
mutation
any change to the DNA sequence is classified as a mutation. It can range from a single base change to removal of one segment of a chromosome.
meiosis
produces gametes with unique combinations of alleles, thus increasing the genetic variation of individuals within the species.
sexual reproduction and random fertilisation
the combination of gametes is random and results in a zygote that has genes from both of its parents.
when are mutations harmful
those which cause a gene not to function properly or not to function at all. (non sense mutations)
what are missense mutations
may cause variation that benefits the organism by changing a codon, which in turn alters the protein.
what are silent mutations
when the codon still codes for the same amin oacid, so no natural change in the protein occurs. no effect
how does meiosis produce variation
crossing over on homologous chromosomes
chromosome lineup
evolution definition
the change in the frequency of an inherited trait in a population over time
allele
version of a gene
natural selection def
Differential survival and reproduction of individuals with favourable traits in the current environment.
survival of the fittest definition
Fitness refers to the ability to survive to reproductive age,find a mate,and produce offspring, not now big or strong an organism is.
Heritable characteristics are
the characteristics that an organism possesses due to its genetic make-up. These characteristics can be inherited by the organism’s offspring.
macroevolution
occurs on a large scale leading to the development of new species.
Natural selection :
Natural selection occurs when species have variation and certain traits are selected because they help the species to reach a reproductive age and pass on their genes.
Selective breeding :
A form of artificial selection in which organisms with certain characteristics are chosen by humans because they are of some benefit. These organisms are bred to produce offspring that have the same genes and, therefore, the same characteristics.
breed
a group of animals within a species that have specific and simialr characteristics
