8. Chapter 7: Geographic Variation & Speciation (1-26)

Question 1

What is an example of inter population genetic variability?

Answer 1

One species can have multiple populations, where individuals of each population have a tendency to mate with members of their own population which is an example of positive assortative mating. Ex. Porcupine herd and forty mile herd caribous

Question 2

What are models of geographic variation? Examples?

Answer 2

Polymorphic species: species formed of several
geographic groups which differ from each other by traits that are easy to recognize.
Ex. White-tail deer in Ontario/Quebec vs Costa Rica, larger vs smaller
Greater racket-tailed drongo range in traits based on their geography, higher regions have larger feather on head

Question 3

What is an ecogeographic rule?

Answer 3

models of geographical variation that follows climatic gradients for many species within a group of vertebrates

Question 4

What are types of ecogeographic rules?

Answer 4

1. Bergmann’s Rule: populations of endothermic animals living in northern regions of the geographic distribution of the species will generally have a larger size. It is followed by 72%of birds and 65% of mammals
2. Allen’s Rule: In birds and mammals, northern populations/species will generally have short and massive extremities (to conserve heat), whereas southern populations will have longer and thinner extremities (to lose heat).
3. Gogler’s Rule: darker pigments in more humid climates

Question 5

Describe the evolution of fur loss and skin colour in humans.

Answer 5

1. 6-7 Myr ago, the hominines (all human species) shared a common ancestor with the chimpanzee of pale skin covered in a dark fur.
2. 3.7-3 Myr, the A. afarensis lived in tropical forests, were bipedal and arboreal, their diet revolved around fruits, tubers, and leaves, and they lived a sedentary way of life.
3. 3 Myr, there was important cooling, droughts in east Africa, and formation of savanna’s which all impacted the hominin species
4. 1-2 Myr, the H. erectus added meat to their diet as there was less fruit available, they needed to walk longer distances for prey and water resulting in a more active lifestyle that of a hunter-gatherer becoming adapted to life on plains. Natural selection acted on the shape of the body for its ability to run attracting bodies with an abundance of sweat glands of less fur to have more efficient thermoregulation.
5. 1.2 Myr, selection in favour of darker skin favouring individuals with thicker, darker, and more acidic skin thus individuals with more melanosomes and melanin giving protection against ultraviolet rays, drought, bacterial attacks, and vitamin deficiencies occurs at the same time as fur loss
6. 1.2 Myr to 100,000 years ago the skin of all hominins species including Homo sapiens was dark
7. 100,000 years ago was the great human migration where humans invade to northern habitats
8. 40,000 years ago, evolution of paler skin to maximize UV absorption in areas where UV radiation is weak for adequate synthesis of vitamin D3 by the skin
9. 10,000 to 15,000 years ago humans were able to colonize areas with an important annual deficit of UV rays because they compensated for deficiencies in vitamin D3 through diet (of fishing, hunting, and domestication)

Question 6

Discuss the differences between human glands and a furry animal’s glands.

Answer 6

Furry animal glands:
1. Predominantly sebaceous and apocrine glands
2. Oily sweat
3. Perspiration is difficult
Human glands:
1. Predominantly eccrine glands
2. Watery sweat
3. Perspiration is easy up to 10L/day

Question 7

Thermoregulation/sweating in horses vs carnivores vs humans

Answer 7

Horses: sweating is difficult as there are few eccrine sweat glands, horses sweaty latherine which is a protein of eccrine and apocrine sweat glands
Carnivores: regulate body temperature through panting and sweat through the pads of their paws where their eccrine sweat glands are located
Humans: can easily sweat up to 10L of sweat as we have a lot of eccrine glands as fur was lost to facilitate sweat evaporation

Question 8

Which inherited traits gave those who had it a positive adaptation of survival and differential reproduction compared to other members of the population who didn’t have those traits?

Answer 8

1. Folic acid + Dark skin:
   Folic acid known as vitamin B9 will be destroyed in skin from too much exposure to excessive UV rays. A deficiency in folic acid will have :
2. serious and potentially lethal developmental malformations like spina bifide
3. poor wound healing
4. disturbed immune system
5. sperm malformation
   A vitamin deficiency at a young age or in pregnant women can have a direct impact on the survival and reproductive success of the individual. Thus it’s an adaptation because we can say that dark skin offers a protection against the UV rays that offers a survival and reproductive advantage
6. Vitamin D3 + pale skin: vitamin D3 is synthesized in the skin by UV rays. Vitamin helps in the absorption of calcium in the gut. A deficiency in vitamin D3 would have a direct impact on the reproductive success of affected individuals. Thus it’s an adaptation because pale skin in low UV radiation regions would maximize the absorption of UV rays and the survival of human population in areas of UV deficiency.

Question 9

What is the conclusion of the evolution of fur loss and skin colour in humans?

Answer 9

1. Loss of fur in hominins is linked to lifestyle changes due to climate change, more than 1,2 Myr ago. dark for more than 1 Myr.
2. The skin color became dark quickly after the loss of fur. The skin remained
3. The evolution of pale skin in some human population is linked to the
   colonization of habitats further north during the last 100 000 years. This paler skin is an adaptation to maximize the absorption of UV rays in zones where radiation is low; this allowed the healthy synthesis of vitamin D3. As individuals with darker skin in regions of high UV intensity synthesize Vitamin D3 skin at a much slower rate than individuals with pale
4. A selective advantage of darker skin in regions of high UV intensity is to minimize the degradation of folic acid by UV rays.

Question 10

How is the colour of skin determined (what does it mean/ what is it)?

Answer 10

Skin colour is a variable polygenic trait which explains the variability of pigment intensity. It is an adaptation to UV radiation and is only an indicator of the environment in which populations have lived.

Question 11

What is the morphological species concept?

Answer 11

Is a concept that stems from Aristotelian essentialism.
Consists in bringing together individuals possessing similar and unique morphological traits, under one species name. Specimens belong to a species if they morphologically resemble the “type” specimen (or holotype) of the species. This type specimen is determined by the taxonomist as being a typical specimen showing all the unique features of a species. It is a holotype.

Question 12

How is morphological variability of a species (Darwinian concept) documented?

Answer 12

morphological variability of a species documented through the description of other specimens (paratypes). These specimens usually represent the morphological variability observed in the species.