Mammals

Question 1

What are the 3 mammalian groups?

Answer 1

Placental, marsupial and monotreme.

Question 2

What is a monotreme?

Answer 2

A mammal that lays eggs.

Question 3

What is a marsupial?

Answer 3

A mammal that has a pouch in which to carry their young which are born earlier than in placental mammals.

Question 4

What is a placental?

Answer 4

A mammal that is nourished in the mother’s uterus and born developed.

Question 5

What are some unique mammalian traits?

Answer 5

3 ear ossicles + a cochlea.
True heterodonty.
Hair.
Mammary glands/tissues in females.
Well-developed facial musculature.

Question 6

From what anatomical structure are mammalian inner-ear bones derived?

Answer 6

Ancestral reptile-like jawbones.

Question 7

How has the mandible of modern mammals become simplified from pre-mammalian cynodonts?

Answer 7

Cynodonts possessed a lower jaw made up of 7 bones. In contrast, modern mammals have a lower jaw made up of 1 bone.

Question 8

What is the group synapsida?

Answer 8

Not reptiles but a phylogenetic group that includes mammals and early mammal-like lineages.

Question 9

What drove the evolution of the mammalian ear?

Answer 9

Feeding pattern changes caused changes in the jaw structure leading to improved high frequency hearing.

Question 10

Describe the features of Cetacea.

Answer 10

Mostly marine, some freshwater.
Highly intelligent + social.
Vertical tail propulsion.
Vestigial pelvis.
1 or 2 blowholes.

Question 11

Describe Pakicetus, the earliest cetacean.

Answer 11

Wolf-sized, terrestrial/semi-aquatic mammal.
Whale-like premolars.
Molars resemble terrestrial vertebrates.
Found around streams/rivers 48-52 mya.

Question 12

What are artiodactyls?

Answer 12

The even-toed ungulates. They bear weight on an even number of toes. Includes pigs, hippos, deer, sheep, cattle and cetaceans.

Question 13

Describe Ambulocetus natans.

Answer 13

Sea lion sized.
Inefficient walker but strong swimmer.
Spine undulation + hind feet propulsion.
Found coastally around 49 mya.

Question 14

Describe Rodhocetus kastani.

Answer 14

Reduced hind limbs.
Limb/Trunk swimmer with a longer, flexible vertebral column.
Found in shallow offshore habitat 46-47 mya.
Higher, farther back nostrils.

Question 15

Describe Doradon.

Answer 15

Greatly reduced hind limbs.
Hands used as flippers.
Whale-like teeth.
Flattened caudal vertebrae.
Found in marine environments around 37 mya.

Question 16

Describe the group Rodentia.

Answer 16

Make up 50% of mammals.
Lack canines but have 2 very large incisors.
Nearly exclusively herbivorous.

Question 17

Describe the group Carnivora.

Answer 17

Highly diverse.
Meat eaters.
Highly developed canine teeth.

Question 18

Describe the group Cetartiodactyla.

Answer 18

Includes Artiodactyla + Cetacea.
Hooves with even-numbered toes.
Mostly ruminants with 4 chambered stomachs.

Question 19

Describe the group Perissodactyla.

Answer 19

Odd-numbered toes.
Cellulose digestion occurs in the intestines.
Only includes horses, asses, zebras, rhinos and tapirs.

Question 20

Describe the group Primates.

Answer 20

Highly developed brains.
Often bipedal.
Shoulder gurdle.
High visual acuity, reduced sense of smell.

Question 21

What is the common term for the group Hominidae?

Answer 21

The great apes.

Question 22

Which came first, upright posture or larger brains?

Answer 22

Upright posture.

Question 23

What is the foramen magnum and what is it’s evolutionary significance?

Answer 23

It is an opening in the skull where the spinal cord exits the cranial cavity. It has been found that the foramen magnum appeared on the underside of the skull before brain enlargement.

Question 24

How do humans compare in terms of intraspecific sequence divergence to other apes? What does this show?

Answer 24

Humans show very little sequence divergence compared to other apes suggesting we have gone through an evolutionary bottleneck.

Question 25

What are the 2 theories of human expansion?

Answer 25

The Out-of-Africa Theory and the Multiregional Theory.

Question 26

What were the 2 Out-of-Africa events?

Answer 26

Homo erectus around 1.8 million years ago and Homo sapiens around 50,000 years ago.

Question 27

What is the Multiregional Model?

Answer 27

The theory that archaic Homo in different places around the world independently developed into Homo sapiens.

Question 28

Which theory of human expansion is favoured? What evidence supports this?

Answer 28

The Out-of-Africa Theory. The 3 earliest branches of Homo sapien exclusively lead to sub-Saharan lineages; only the 4th branch contains African and non-African lineages. Human Y chromosome phylogeny shows African is the oldest lineage.

Question 29

When was the last common ancestor of Neanderthals and Homo sapiens?

Answer 29

Around 500,000 years.

Question 30

Why do long shared haplotypes tend to be recent but short shared haplotypes tend to be older?

Answer 30

Haplotypes are broken down over time via recombination.