A4.1 evolution and speciation Flashcards
evolution
the process of cumulative change in the heritable characteristics of a population
or
the change in gene frequency in a population over time
in order to have evolution there must be variation
darwinian evolution vs. lamarckism
darwin and wallace’s theory of evolution by natural selection: gene mutations occur and if the characteristic if favourable it will persist through evolution.
this replaced a previous idea formulated by Lamarck that organisms acquired characteristics in their lifetime and passed them on to their offspring
microevolution
small allele changes within a single group, small amount of time needed
macroevolution
large changes of a group/s that can result in speciation, large amount of time needed, made up of lots of microevolutionary changes
evidence for evolution
- similarities in base sequences in DNA or RNA and amino acid sequences in proteins between species implies common ancestor
- shared genetic code implies a common ancestor
- all organisms in the same domain have the same cell structure
- selective breeding
- homologous and analogous structures
- vestigial structures
selective breeding as evidence for evolution
selective breeding is when breeders choose to breed specific organisms with the most agriculturally desirable genetic characteristics
although selective breeding is a human choice, it is still evidence that evolution is happening as a result of an accumulation of small changes over time. If this can be achieved artificially, it is reasonable to assume that it could happen naturally through natural selection.
these artificially selected breeds are clearly related and can still interbreed with wild species
variation between different domesticated animal breeds and varieties of crop plant, as well as between them and the original wild species shows how rapidly evolutionary changes can occur
homologous structures as evidence for evolution
homologous structures are structures derived from the same body part of a common ancestor.
organs that may have different functions but exhibit structural similarities as a result of the presence of a common ancestor, usually the result of divergent evolution.
specific example: pentadactyl limbs (five finger bone structure) in humans, horses, moles, bats. the basic structure is the same but the functions may be different
analogous structures as evidence for evolution
structures that have superficial morphological similarities, however a detailed study of their morphology reveals significant differences. They may serve the same function and are a result of convergent evolution and thus the species do not have a common ancestor.
evidence of evolution because they have developed independently to environmental conditions to have the same needs.
convergent evolution
the origin of analogous structures: if a feature such as wings is seen in many different organisms such as bats and birds, then it is clearly advantageous and could have evolved in multiple ways over time
speciation
the only way in which new species have appeared: the process of creation of a new species through isolation and adaptation to different challenges and environments
speciation increases the total number of species on Earth, and extinction decreases it (99.9% of species that have ever lived on Earth are extinct)
gradual evolutionary change in a species is not speciation
role of reproductive isolation and differential selection in speciation
reproductive isolation: when individuals initially from the same species but now from two separate populations will not be able to reproduce with each other successfully to produce fertile offspring.
geographical isolation: when physical barriers such as land or water formations prevent males and females from different parts of a population finding each other, thus making interbreeding impossible.
geographical isolation, temporal isolation, and behavioural isolation are all means of achieving reproductive isolation.
specific example: the separation of bonobos and common chimpanzees by the congo river
bonobos and common chimpazees as an example of reproductive isolation
the congo river, a physical barrier that prevents the two populations of primates from interacting or interbreeding.
- primates on the north and east of the river are chimpanzees
- primates on the south of the rivers are bonobos.
the differences in habitat, availability of food and the presence of enemies such as snakes have led to differences in traits, specifically behavioural traits, between the two separated populations.
chimpanzees= more aggressive + territorial
bonobos= more peaceful and nomadic
chimpanzees= patriarchal structure
bonobos=matriarchal structure
they exhibit differential selection: when one environment favours certain traits while another favours different ones.
allopatric vs sympatric speciation
allopatric speciation when a new species forms from an existing species because the population is separated by a physical barrier. geographical isolation leads to allopatric speciation
sympatric speciation when a new species forms from an existing species living in the same geographical area, caused by temporal or behavioural isolation.
temporal isolation: populations or species become reproductively active at different times throughout the year
behavioural isolation: populations of a species have differences in behaviour that prevent interbreeding, e.g mating rituals or attraction
adaptive radiation
adaptive radiation is defined as a pattern of diversification in which species that have evolved from a common ancestor occupy a range of ecological roles.
characteristics that make an individual suited to its environment or way of life are adaptations, which happen as structures evolve over time to fit their functions more and more closely.
adaptive radiation is a source of biodiversity.
it allows closely related species to coexist without competing, thereby increasing biodiversity in ecosystems where there are vacant niches
