U3 Case Studies Flashcards
Skin Color Case: Overall Phenomenon
Wherever UV is strong, skin is dark
And wherever UV is weaker, skin is lighter
The skin color phenomenon suggests that…
Variation in human skin melanin production arose as different population adapted biologically to different solar conditions
Melanin
Pigment in our skin
–> Absorbs and reflects light rays
Folate
B Vitamin (needed for healthy embryonic development and sperm production)
What does sunlight do to folate?
Breaks it down
How does melanin relate to folate?
Melanin protects from UV radiation which in turn protects from folate breakdown
Vitamin D Purpose
Calcium absorption
What do we need to produce Vitamin D?
UV-B rays
Skin Color Case:
High Sun Areas = ________ (and why?)
Dark Skin
–> Provides > protection from folate breakdown while also having enough sun exposure to produce vitamin D
Skin Color Case:
Low Sun Areas = ________ (and why?)
Light Skin
–> Provides > absorption of UVB rays to get vitamin D while also providing enough protection from folate breakdown
Lactose Intolerance Case
All infant mammals can digest dairy through the lactase enzyme however many stop producing lactase as they age
HOWEVER, certain areas have populations of “lactase persistent” people
The lactose intolerance case is due to…
2 separate/distinct mutations that arose INDEPENDENTLY of one another
Where did the mutations of lactose intolerance originate from?
Populations in Western Europe and Western Africa evolved INDEPENDENTLY to be lactose intolerant
Lactase persistance provided a…
selective advantage (in areas with cattle)
–> (Unlike SE Asia which didn’t have cattle)
Elephant Tusks Case: Purpose of tusks
Utilized to:
1) Dig for water
2) Strip bark off trees
3) Males to compete for females
Tuskless males are rare because…
Without tusks, in fights for females they can get seriously injured
Poaching
Elephants WITH tusks were/are killed for the ivory in their tusks
Increase in poaching caused…
a decrease in the male population of elephants with tusks
–> Cause an increase in the population of tuskless elephants
Why did tuskless elephants become more populous?
The tuskless elephants were more likely to survive as they were not targeted by poachers
–> Increased their survival which then increased their reproduction
Mouse Coloration Case
Darker mice are found in regions with dark lava flows
Lighter mice are found in sandy deserts
Benefits of dark fur in a dark environment
Allowed the mice to better blend in with the surroundings: less obvious targets to predators
Bird of Paradise
Males:
–> Black with bright turquoise feathers that fluff out to form what looks like a frowny face
Females:
–> Simple brown feathers
(Female chooses mate)
Red Capped Manakin
Males:
–> Have a bright red head, black feather body, and practically neon-yellow legs
–> Snap their wings and do a quick dance
Females:
–> Dull olive-green colors which resembles brown
(Female chooses mate)
Ibex
(A type of wild mountain goat)
Males: Enormous horns on head
–> Used to fight other males for females
Females: Small horns
(Male-male competition determines mate)
Horned Beetle
Males: Have large horns and are overall bigger
–> Used to fight other males for females
Females: Smaller and no horns
(Male-male competition determines mate)
Anolis Lizard: Pre-Zygotic Isolation
A lizard species that has a Dewlap (flap of skin below animal’s neck used to attract mates)
–> Changes to this dewlap leads to new species as females wouldn’t recognize different dewlap as being part of their species (not attracted)
Orca: Pre-Zygotic Isolation
Orcas are highly intelligent and live in groups (CULTURES)
–> Different orca cultures eat different foods (fish or mammals) and this separates cultures geographically from each other
–> Orca cultures have different dialects to their sounds
Altogether: Prevents different orca cultures from interacting with one another
