Theme A: A4 Ecosystems - A4.1 Evolution and Speciation Flashcards
evolution
the process of CULMATIVE change in the HERITABLE characteristics of a POPULATION.
modern synthesis theory (neo-Darwinism)
The modern synthesis theory combines Darwin’s theory of evolution by natural selection with Mendell’s work about genetics.
Lamarckism (Lamarckian evolution)
organisms acquired characteristics through time and then passed them onto their offspring.
selective breeding
breeders choose the males and females with most agriculturally desirable genetic characteristics and breed them together.
artificial selection
farmers and breeder choose which animals will reproduce together and which will not. (A broader concept of human-influenced trait selection.)
homologous structures
structures derived from the same body part of a common ancestor (e.g. five-fingered limbs in humans, bats, and whales) yet they serve compltely different functions. Darwin explained that these were evidence thatorganisms have anad eveolve from a common ancestor.
pentadactyl limbs
“penta” meaning five, and “dactyl” meaning fingers. the shape and number of bones may vary and the specific function may be very different, but the general format is the same.
analogous structures
structures that may have the same function but don’t necessarily come from the same body part and do not indicate a common ancestor.
phylogeny
The evolutionary history and relationships among species or groups of organisms, typically represented as a phylogenetic tree, which illustrates common ancestry and divergence.
convergent evolution
The process by which unrelated or distantly related organisms independently evolve similar traits or adaptations in response to similar environmental pressures or ecological niches. Examples include the wings of bats, birds, and insects.
divergent evolution
The process by which two or more related species become increasingly different from their common ancestor, often due to adapting to different environmental pressures or ecological niches.
marsupial
A subclass of mammals (Marsupialia) characterized by giving birth to relatively undeveloped offspring, which then typically continue to develop inside a pouch (marsupium) on the mother’s body.
natural selection
A process in which individuals with advantageous heritable traits are more likely to survive, reproduce, and pass on these traits to offspring, leading to changes in the traits of a population over generations.
reproductive isolation
in some situations, member of the same species can be prevented from reproducing because there is an insurmountable barrier between them. Can be geographical, temporal, or behavioural barrier.
geographical isolation
happens when physical barriers like land or water formations, prevent males and females from different parts of a population from finding each other, thus making interbreeding impossible.
example: a river mountain, a clearing in a forest. man made barriers also exist like roads, dams, the great wall of china, etc. a more specific example is the Congo River which acts as a physical barrier that prevent 2 populations of primates from interacting/interbreeding. the primates to the north and east of the river are chimpanzees and the bonobos are to the south. differences in food, enemies, habitat have lead to differences in traits, notably behavioural traits.
differential selection
when one environment favours certain traits and another environment favours different traits, there is differential selection.
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. In this case, speciation can be caused by temporal or behavioural isolation.
temporal speciation
refers to incompatible time frames that prevent populations or gametes from encountering each other. (e.g. if one population of mammals is hibernating or has not returned from migration when another population of the same species is ready to mate, this would form a temporal barrier between the two gene pools. OR if female parts if flowers from one population reach maturity earlier or later than the release of pollen from another population, the 2 will find it difficult to produce offspring.)
behavioural isolation
when part of the population develops a different behaviour that isolates it from the rest of the population. it can happen when one population’s lifestyle is not compatible with those of another population. (e.g. if part of a population of songbirds gradually develops a different song to attract mates, then over time that part will only mate with those that recognise its song. another example considers courtship behaviour).
adaptive radiation
Adaptive radiation describes the rapid evolutionary diversification of a single ancestral line. It occurs when members of a single species occupy a variety of distinct niches with different environmental conditions.
textbook: allows cloesly related soecies to coexist withou competing, thereby increasing biodiversity in ecosystems where there are vacant niches.
niche
a position or role within a community.
locus
a genes positon in a chromosome.
courtship behaviour
A set of display actions or rituals performed by animals to attract a mate, which often ensures species recognition, assesses mate quality, and increases the likelihood of successful reproduction.
polyploidy
when a cell contains 3 or more sets of chromosomes. results in very rapid speciation (a.k.a. abrupt speciation) where the new organism has such different chromosome number from its parents that it is reproductively isolated. arises during the production of sex cells: if copies of chromosomes are not completely separated into distinct nuclei, they will end up in the same cell. can follow the principle of sympatric speciation
why are hybrids sterile?
when a sperm cell fertilises an egg cell its chromosome 1 needs to be compatible with the egg’s chromosome 1. each gene’s position, its locus, needs to match in order to allow the genetic information from each parent to contribute to the offspring’s features. the same compatibility and matching is needed fir ALL the chromosomes in the organism for viable offspring.
hybrids often have an odd number of chromosomes. this mismatch of genes and chromosomes makes the production of egg an sperm cells difficult if not impossible. this mismatch explains the infertility of interspecific hybrids.
advantages of polyploidy
1) can allow sterile hybrid plants to become fertile again.
2) extra genetic material can give plant an advantage over others.
how is a species formed?
through natural selection and the presence of some kind of reproductive isolation, a new species can evolve. just evolving overtime is NOT enough; there must be a split whereby two populations are isolated and exposed to different environments that will select for some traits over others.
