A4.1 ecosystems unity and diversity Flashcards
what is evolution
the process of cumulative change in heritable characteristics of a population
punctual vs gradual evolution?
- punctual evolution is very short and rapid periods of change followed by long periods of stability. for example, the theory that human evolution was abrupt.
- gradual evolution is when changes occur slowly and gradually over time. for example, elephant acquiring larger ears over time.
explain speciation
Speciation is the process by which a population becomes split, and each group evolves differently over time, leading to the formation of new species.
This is possible because variation exists within a population When a population becomes reproductively isolated by factors like a geographical barrier like a river, both groups are exposed to different environmental conditions or selective pressures.
Over time, the two groups evolve differently as different mutations affect both groups, this is referred to as differential selection. These differences between the populations act as barriers to gene flow.
Over time, the groups evolve so differently that they can no longer interbreed and are two distinct species.
what is darwinism?
Darwin proposed the idea that (theory of evolution by natural selection)
- Individuals in a species show a wide range of variation due to random mutations in their DNA
- Individuals within a population must compete for survival due to selection pressures
- Individuals with characteristics most suited to the environment have a higher chance of survival and are more likely to reproduce
- Advantageous alleles are passed down to offspring
- Over many generations the advantageous alleles become more frequent in a population
Overall, this theory suggests that traits are then heritable
how are some points of darwins theory proven to be slightly incorrect?
through genetic sequencing, his theory may be disproved in a few ways because:
- there can be abrupt evolution, for example, we know that antibiotic resistance can evolve in bacteria very quickly
- fossils can prove to show intermediate species
- because of evolutionary change within geological time periods, we cant prove if natural selection actually has given rise to species.
what is modern synthesis?
referring to Darwin’s theory of evolution, modern synthesis explains how evolution is affected by factors like genetic variations, breeding, isolation, natural selection.
what is lamarckism?
Lamarcks theory entailed that the changes (acquired traits) that the organisms go through during hteir lifetime, can then be passed on to offspring.
For example giraffes having long necks because of the need of having to reach the branches of the trees.
what is natural selection?
Natural selection acts on genetic variation in populations. over some period of time, species with more advantageous traits based on their environment are more likely to reproduce and pass on the beneficial alleles responsible, and therefore survive. Ultimately, that trait would then become more frequent in a population.
what is selective breeding/ artificial selection? example
when humans choose the desirable traits of an organism and breed them together repeatedly to increase the traits over the next many generations.
E.g: a cow being bred to have a straight back, since its more beneficial for birthing, and milking.
describe process of selective breeding
- population shows variation
- breeders select the ones with desirable traits
- two selected individuals are bred together
- the offspring is tested for the beneficial traits, and if displayed to the greatest extent they’re selected for further breeding
- the process is repeated until most offspring display the desirable traits.
what is a plant breeding example
10k years ago farmers started saving seeds from plants with most desirable characteristic (larger ears and more kernels), and only planted those the following seasons.
what is selection pressure?
the features of a species’ environment that impact their ability to survive/ reproduce
example: a predator is a selection pressure
homologous structure example
- body parts that appear and function differently but share structural similarities / structures derived from the same body part of a common ancestor
- direct example is limbs of animals, as the basic arrangement of their bones in diff types of limbs is very similar in : bats, birds, crocodiles, whales, horses, and monkeys.
an explanation for this phenomenon can be adaptive radiation.
explain the pentadactyl limb(homologous structure example)
- any limb that has five digits
- the pentadactyl limb has a similar bone structure but enables the organism to move in a diff way
E.g: the human foot for walking/running, whale flippers for propelling themselves, bird wings for flying, limbs of frogs to jump, alligator limbs to walk and swim etc
Although the individual bones of the pentadactyl limb in these example animals are very different shapes and sizes due to their different mechanisms of locomotion, their layout is almost exactly the same
analogous structure example
Analogous structures are characteristics with similar form and function, but with different evolutionary origin. For example bats and birds
what is convergent evolution? example
(evolve separately, adapt to similar environment)
- when two distantly related species live in habitats with similar selection pressures, meaning that similar traits provide survival advantage. Furthermore, those traits can evolve separately rather than as a result of a single mutation.
E.g : dolphins and sharks
- both share similar body shapes and are aquatic animals
- they belong to diff classes as dolphins are mammals and sharks are fish
–> their body shapes evolved separately rather than originating in one common ancestor.
what is divergent evolution?
when a closely related species acquire enough variations in their traits that ultimately leads to speciation.
example - wholly mamoth and elephant, darwins finches etc.
what is reproductive isolation?
example
- when changes in alleles or phenotypes of an individual in a species prevents them from breeding with other individuals that dont.
for example, fertilization between a tiger and a leopard,
what are some examples of allele or phenotype changes that can lead to reproductive isolation?
- Seasonal changes (temporal isolation)
- some organisms have different seasons of mating or flowering, so they become sexually active at diff parts of the year - Behavioural changes (behavioural isolation)
- some organisms may develop changes in courtship behaviour, meaning they no longer attract others of the opposite sex for mating.
what is geographical isolation (allopatric speciation/ the most common type of speciation) ? example
- when populations of a species become separated from each other by geographical barriers, which then prevent gene flow (body of water, mountain rage, or manmade motorways).
- Over time, the two populations may become so different that they are then reproductively isolated, and speciation has occurred.
example, the congo river dividing bonobos and common chimpanzees.
- because of environmental factors like resources, chimpanzees tend to be more aggressive than bonobos
- chimpanzees have male-dominated social structure, while bonobos have dominant female structures.
this can occur through differential selection that can result in differences between the two populations
what is divergence?
the process in which interbreeding species diverged into more evolutionary groups, therefore becoming more dissimilar over time.
what is sympatic speciation? example
the creation of a new species based on behavioural and temporal isolation.
(change in alleles or phenotype leading to specific changes in behaviour, which prevents them from interbreeding)
What is allopatric speciation?
the creation of a new species based on geographical isolation.
what is adaptive radiation? example
- a rapid evolution of multiple species from a common ancestor
(organisms with homologous structures all evolved from a common ancestor but adapted to diff environments)
- likely to have similar features and be able to live together as they fill diff ecological niches.
examplethe finches
