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Flashcards in adaption Deck (49):
1

adaption

a change or the process of change by which an organism or species becomes better suited to its environment

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when does adaption occur

hone an organism displays traits that allow it to live in a particular environment--> all organisms are

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all organisms are..

adapted to their environment

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historical views

Lamarck and Erasmus Darwin emphasised the role of inheritance in explaining similarities between organisms. Both argued that modifications were gradual and not random, but arose in response to an organisms environment i.e. they adapted

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what idea of charles Darwin brought the idea of adaption to the forefront of evolutionary biology

Natural selection

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Modern synthesis

Neo-Darwinists theory- led by RA fisher, tied the concept of fitness (reproductive success) to those of adaption and natural selection

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role of natural selection in adaption

if the rate of mutation or drift balances selective pressure then it might appear that the population is not under selection

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mutations

explores possibilites, NS defines traits that a re adaptive

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muller ratchet

accumulation of deleterious mutations (which can be removed by sexual reproduction and recombination

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adaptive/fitness landscape

over time pop. move toward local peaks or optima- the process is dynamic and promoted by mutations and is counteracted by drift and introgression

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what promotes adaption

-moderate mutation rate
-a small amount of gene flow
-directinal selection
-developmental competence

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what prevents adaption

-inbreeding
-genetic drift
-large amounts of gene flow
-stabilizing selection

Therefore small populations have less potential for adaption

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the fundamental niche includes

the total range of environmental conditions that are suitable for existence without the influence of interspecific competition or predation from other species

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the realised niche

describes the part of the fundamental niche occupied by the species

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local adaption and NS

any widespread population is likely to experience diff environmental conditions
-as a consequence it will soon consist of a number of sub-population that differs slightly, even considerably
e.g. rat snake, has geographic 'race', that still share a common gene pool

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example of adaption: moths

Evolution of moths has been studied greatly over the past 200 years. Originally the vast majority had light coloration for camouflage (light colored trees). However due to widespread pollution during the industrial revolution, many of the lichens died out and the trees which peppered moth rested on became blackened by soot, causing most of the light-colored moths to die off. Dark colored moths flourished.
¬ Light colored moths (typica) vs. Dark colored, or melanic moths (carbonaria) flourished.
¬ The first cabronaria moth was recorded by Edleston in Manchester 1848, and over the subsequent years it increased in frequency.

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any change in the environment is likely to..

lead to local adaption

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populations consistent of sub-populations because..

any widespread pop. is likely to experience diff environmental conditions in diff parts of its range

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saltationism

a sudden change from one generation to the next, this is large or very large, in comparison with eh usual variation of an organism.

Darwin sad that the evolutionary process must occur gradually, not in salutation, since saltation are not presently obsessed and extreme deviation from the usual would be more likely to be selected against

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who disagreed with the theory of saltationism

Darwin, since saltation are not presently observed and extreme deviations from the usual phenotypic variation would be more likely to be selected against

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cambrian explosion

most major animal group appear for the first time in fossil record some 545million years ago (on the geologic sale this is a relatively short time period)--> a time known as the cambrian explosion

There was once many more body plans
- 545mya a sudden diversity of body plans took place

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evidence for cambrian explosion

many strange fossils have been found and can be dated to around 545 mya

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what leads to macro evolution

saltation

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advocates of salvationism deny the

Darwinian idea of slowly and gradually growing divergence of character as being the only source of the evolutionary process

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saltation simple

sudden discontinuous ad crucial changes -macro mutations

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macro evolutions are said to be responsible for the appearance

if new higher taxi including class and order

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microevolution is thought to be responsible for

the fine adaption below the species level

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hopeful monster hypothesis

suggests that major evolutionary transformation have occurred in large leaps between species due to macromutation

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micro/macroevolution is characterised by two extremes

1. gradualism- evolution generally occurs uniformly and by steady and gradual transformations
2. punctuated equilibrium- evolution is marked by isolated episodes of rapid speciation between long period of little or no change

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gradualism

evolution generally occurs uniformly and by steady and gradual transformations

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punctuated equilibrium

evolution is marked by isolated episodes of rapid speciation between long periods of little or no change

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we can look at homologous structures found in the fossils of extinct species and

infer their function by looking at homologues structures in species that do exist eg. claws of dogs and cats have similar functions and structures

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why must we take great care in establishing function of traits found in extinct species

analogous structures in unrelated species e.g. fns on fish, whales and cuttle fish where there is no common descent

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homologous structures

similarity by common descent, similar function and form, similar development trajectory

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analogous structures

diff ancestry, same function, diff developmental trajectory

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exaptation

adaptation that involves new uses for existing traits
e.g. malleus and incus wer originally part of the lower jaw of reptiles required for chewing

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co-opted traits are the same as

exaptation

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linked traits

traits may be selected for because they are linked to something else. e.g. a certain unuseful gene may be linked to a very useful gene

e.g. genetic hitchhiking occurs when an allele changes frequency not because itself is under NS, but because it is near another gene that is undergoing nS

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Dr Pangloss

believed evolutionary solutions are not optimal

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example of an imperfect design (Dr Pangloss)

te male urogenital system.
during the evolution of mammals, testes moved from an internal position to a specialised structure outside the body, the scrotum
o Whilst the sperm duct passes ventral to the ureter, the testis migrates dorsal to the ureter during development, requiring a lengthening, not a shortening of the sperm duct

o A more efficient design would be migration of the testis on the same side of the ureters the sperm duct
-progressive adaption

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once a pathway of progressive adaptations begins

reversals may become competitively disadvantageous or diff to achieve

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Doll's law

evolution is not reversible i.e. structures or function discarded during the course of evolution do not reappear in a given line of that organism

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criticism of the 'adaptionist adgenda'

adaptationists seek to find adaptive explanation for every characteristic of an organism, however some things ar not 'for' the 'purpose' etc they seem to be filling.

Somethings that exist are not adaptive- selectively neutral e.g. ear lobe

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maladaptations

more harmful than helpful, in contrast with an adaptation, which is more helpful than harmful.

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sickle cell and maladaptations

o Heterozygosity (HA/HS) or sickle trait leads to some resistance to malaria infection. fitness advantage
o Homozygosity (HS/HS) however leads to premature death
In one setting the trait is advantageous, in another its deleterious and maladaptive.

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summary of adaption

occurs when an organism displays traits that allow it to live in a particular environment - all organisms are adapted.
-adaptation is a by-product of NS
-requires a balance between mutation , genetic drift and introgression
-there has previously been much greater diversity
-evolutnitonary solutions ar imperfect, not optimal
-we have to be wary of speculation and just so stories

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there are many ideas about adaption since

there are many evolutionary biologists

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evolution of the Eye-Eye

Some scientists think this is how the eye has evolved:
o Simple light sensitive spot on the skin of some ancestral creature gave it some tiny survival advantage, perhaps allowing it to evade a predator. Random changes then created a depression in the light sensitive patch, a deepening pit that made “vision” a little sharper. At the same time, the pits opening gradually narrowed, so light entered through a small aperture, like a pinhole camera.
o Every change gave a survival advantage, no matter how slight. Eventually the light sensitive spot evolved into a retina, the layer of cells and pigment at the back of the human eye. Over time a lens formed at the front of the eye
o In fact, eyes corresponding to every stage in this sequence have been found in existing living species. The existence of this range of less complex light-sensitive structures supports scientist hypotheses about how complex eyes like our could evolve.
o The evolution of the eye is estimated to have taken 364,000 years.

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darwin theory and the human eye

when evolution skeptics want to attack Darwins theory, they often point to the human eye. How could something so complex, have developed through random mutation and natural selection? Even after millions of years

-If evolution occurs through gradations, how could it have created the separate parts of the eye- lens, retina, pupil- since none of these structures by themselves by would make vision possible? In other words, what good is five percent of an eye?
-Darwin acknowledged from the start that the eye would be a difficult case for his new theory to explain- but not impossible. Through NS diff types of eye have emerged in evolutionary history- and the human eye isn’t even the best one. Because blood vessels run across the surface of the retina instead of beneath it, its easy for the vessels to proliferate or leak and impair vision. So, the evolutional theorist say, the anti-evolution argument that life was created by an ‘intelligent designer; doesn’t hold water if: if God or some other omnipotent force was responsible for the human eye, it was something of a botched design