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Chapter 3

LIFESCI 2D03 Chapter Notes - Chapter 3: Proximate And Ultimate Causation, Endocrine System


Department
Life Sciences
Course Code
LIFESCI 2D03
Professor
Brett Beston
Chapter
3

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Immediate causation is proximate causation
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Ultimate causation is when a trait has formed due to evolution
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In proximate causation we answer questions like What and How
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Proximate
Ultimate
Behavior
In proximate causation we are working with factors that are affecting the organism here and now- within it's lifespan, no history or future is
considered
-
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Proximate analysis will help us understand how evolution has helped shape human aggression
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Geoff Hill worked on house finches (carpodacus mexicanuus)
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He started his experiment knowing that the coloration of the bird's feather is due to carotenoid - color pigments ingested by birds. Meaning they
completely rely on their diet for their coloration
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Which meant that coloration of their plumage was due to Development Differences in what the males ate as they matured
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One set of female birds were fed a normal apple and the other set were fed carotenoid.
The birds fed the carotenoid turned a brighter plumage whereas the birds fed the normal apple stayed the same.
This experiment was based on female birds:
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What causes the plumage color to change for the females between populations?
1)
What causes coloration differences between males and females?
2)
This arose 2 questions:
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To answer question #1 Hill found that the color of female population is difference based on which locality the birds are from. This was due to the
amount of carotenoid containing food that was available in the area.
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For question #2, males are always looking for carotenoid based food than females that is why their plumage is much brighter
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This leads to an ultimate question about why do females not seek for carotenoid-rich food. The answer simply being that they do not benefit from
bright plumage like males do, and only care for calorie intake.
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In his experiment Hill found out that the brighter the plumage of a male the higher their chances of finding a mate. But why was this?
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Brighter colored females are better at fighting off pathogens. Meaning they will not contract any infections from the duller colored finches.
Furthermore this resistance can be hereditary and be passed down to their offspring.
1)
Experiments have also shown that the brighter plumage finches feed their young ones more than duller colored male finches
2)
Another common sense thing would be: brighter plumage males are better foraging, this better foraging trait is also hereditar y. As the color
of the plumage is solely depended on diet.
3)
The female finches chose bright colored males for three reasons:
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Hormonal
1)
Neurobiological
2)
Molecular genetic
3)
Developmental
4)
Proximate Causation is depended on 4 factors:
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Depended on the endocrine system, which is composed of ductless glands that secrete hormones directly into the blood stream
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The endocrine system directly effects behavior
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Hyposecretion: diminished secretion
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Hypersecretion: excessive secretion
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There are also neurohormones that are secreted into the blood stream by neurons (they have ducts)
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Hormones are secreted into the bloodstream and via the bloodstream these hormones can reach almost every cell in the body but can only
interact with cells that have receptor sites, meaning the endocrine system only effects behavior when these lock and key models interact.
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Both gene expression and protein synthesis effect directly or indirectly on animal behaviour
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Hormonal & Proximate Causation
The endocrine system reacts with stimuli from the environment & that is when the hormones are secreted into the blood stream. E.g. when days
are longer more testosterone in males is produced as it helps them gain access to females, defend and build nests. As testosterone increases
aggression in males.
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Input - Sensory System
1)
Processing - Central Nervous System (CNS) which processes and integrate the information received
2)
Output - Effectors like muscle movement
3)
Animals possess 3 interactive systems
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Hormonal changes either trigger or modify behavior they may even organize behavior, like rat fetus surrounded by females is less aggressive and
sexually active then male rats surrounded by other males.
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How does the Endocrine system work?
The fight or flight response
Chapter 3
Thursday, September 15, 2011
4:36 PM
LIFE SCI 2D03 Page 1
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