Struggle for Existence part 2 Flashcards
contrary to some popular ideas, evolution should not be ex-pected to produce perfection. True
True
Adaption through ________
natural selection
Purpose of pencil to write and ear is to hear, both become better adapted through action of ________
selection that eliminated variants that served purpose less effectively
Purpose there, plan absent
A modern biologist recognizes no element of proper planning the origin and evolution of the human ear. -Ears and other features of living or-ganisms…are perfected entirely by the trial-and-error process of natural selection proposed by Charles Darwin in 1859.
-Ears are main-tained and improved because individuals with better ears are more likely to survive and pass their genes on to future generations. This conclusion is supported by evidence that organisms can have sophisticated ad-aptations and at the same time show…features that would not be there if intelligent planning had played a role.
natural Selection does
select new variants that perform a little better than the previous model and over millions of generations, accumulation of those little improvements can be sublime but imperfections give away the unplanned process of nature
How a feature increases an organism ability to survive and pass on it genes, we call the _____ a function and feature an ________
1) role
2) adaption
Human ear represent an ______ for the function hearing. Why did it arise?
1) adaptation
2) because animals with more acute hearing had HIGHER fitness than other.
Well functioning ears confer a fitness advantage
In many animals, shape and orientation of pinna (external ear) is important to sharpness of hearing. Example?
An alert cat turns its ear to trash sounds but in humans, pinna contributes very little to hearing and certain features have no function
In many animals, shape and orientation of pinna (external ear) is important to sharpness of hearing. Example?
An alert cat turns its ear to trash sounds but in humans, pinna contributes very little to hearing and certain features have no function.
Many animals can regulate body temp in addition to hearing (rabbits, elephants) = vascularized ears dump heat from body to environment through blood flow
Natural selection weeds out the worst trait but ….
it takes time and does not produce perfection
when is Maladaptive trait prominent?
when changing environment with new ecological challenges and opportunities change the fitness consequences of pre existing characteristic
Example of maladaptive trait prominent:
Humans sting attraction to sweet and fatty foods was probably an adaptive trait in past environment where energy rich food was rare
Modern: doughnut rich environment it has become maladaptive
Maladaptive traits can be
lingering holdovers form different environment, and also be mainlines by tradeoffs and constraints
Nothing in the action of natural selection prevents traits from multitasking. True or False
True
Natural Selection does not act directly upon _____ or ____ in isolation
1) traits or genes
Individual organisms are the entitles that succeed or fail, so Adaptive evolution of a particular trait depends on
its overall effect on fitness, through all of fits function
large eared jack rabbit encounters cool climate, small ears….
which smaller ears would allow to retain heat better. Thermoregulation: smaller ears might reduce having sharpness and makes rabbit vulnerable to predators
Tradeoff
Rabbits ear are built, there is a negative relationship between hearing well and conserve heat well
longer ear: cool in summer and hear well but lose heat in winter
small ear: warmer in winter but cannot hear as well as with long ears and become vulnerable to predators
- hamper adaptive finetuning.
Tradeoff
Rabbits ear are built, there is a negative relationship between hearing well and conserve heat well
longer ear: cool in summer and hear well but lose heat in winter
small ear: warmer in winter but cannot hear as well as with long ears and become vulnerable to predators
- hamper adaptive finetuning.
Impossible to develop ear that maximizes hearing and thermoregulation
Life-History traits
Such traits concern the timing of life events (maturation and reproduction) and # of resources individual invest in such functions
- leads to proposition reproduction-survival tradeoff and size-# tradeoff
Reproduction-Survival tradeoff
Investing resources in offspring means they can’t be used in maintaining the body
Size-# tradeoff
if you make more seeds, they have to be smaller
Resource-allocation tradeoff
- one form of evoltionary constraint
- reduce range or kind of adaptation that one might otherwise see
Example: rabbits - they run around in sun and open areas
- have big ears and those who live in the hottest places have largest bodies
Relationship between ear size and environmental temp =
EVOLUTION in ear size has been largely unconstrained by other factors
American Pikas
- do not have large ears*
- live in rocky place and sensitive large ears might get torn between rock and under rock piles
- Mountain tops are cold places (live there), they do not need to loose heat from large ears. Small ears help keep warmth
However global climate changes,
- pikas encountering more heat waves and large ears might be advantageous
- BUT NATURAL SELECTION for LARGER EARS might be countered by constraint posed by the wear and tear of pikas rocky underground style
The Comparative Method
Examine how diff organisms meet environmental challenging in diff ways
When is comparative method the strongest?
When we know how the species are related to each other
Penstemon example
2 flowers species share many characteristics that suit them fro pollination by humming birds.
2 explanations for similarities:
1) 2 species could be close relatives
- similar because they inherited characters by descent from recent common ancestor
- cannot count the 2 bird adapted species are representing 2 separate evolutionary transitions from bee to bird pollination
2) species could be very distantly related and share characters because they have evolutionarily converged under selection exerted by humming birds
- we can infer that both had diff ancestors that were bee adapted and one represents a separate, indecent transition to bird pollination
Phylogenetic trees
evolutionary relationship
