Lecture 19: Deuterostomes 2

Question 1

What are mammals and what are they named for?
Are they endotherms or ectotherms?

Answer 1

Mammals are a monophyletic group of amniotes named for mammary glands, which produce milk.
Milk nourishes developing young (lactation).

All mammals are endotherms (“inside-heated”):
- maintain high body temperatures by oxidizing food
- Body covered with hair or fur made of keratin

Question 2

What are the three groups of mammals?

Answer 2

1. Prototherians (monotremes: platypus and 4 echidna)
2. Metatherians (marsupials: opossums, kangaroos, wallabys, etc.)
3. Eutherians (placental mammals)

Question 3

What is the mammalian placenta?

Answer 3

Placenta nourishes an embryo internally. It is an organ combining maternal and embryonic tissues.

After development period (gestation), embryo emerges from mother’s body

Question 4

Many vertebrate lineages evolved variety of methods of parental care. What are they?

Answer 4

• Fanning aquatic eggs with oxygen-rich water
• Guarding eggs and/or new young from predators
• Keeping eggs and young moist (amphibians) or keeping them warm and dry (reptiles and mammals)
• Supplying young with food
• Teaching survival skills to young

Question 5

What is an advantage and disadvantage of mammals and birds providing particulary extensive parental care?

Answer 5

Advantage: can improve the animals’ fitness by increasing likelihood offspring will survive and reproduce

Disadvantage: energetically expensive to provide

Question 6

Describe feeding, movement, and reproduction for Monotremes and Marsupials and Eutheria

Answer 6

Monotremes: Feed using leathery beak or bill. Swims and walks using webbed feet. Oviparous.
Marsupials:Herbivores, carnivores and omnivores. Crawls, glides, walks, runs, etc. Viviparous with a similar placenta.
Eutheria:Herbivores, carnivores and omnivores. Walks, runs, burrows, glides, etc. Viviparous with extensive placenta. (placental mammals)

Question 7

What are the evolutionary advantages of viviparity and placenta?

Answer 7

1. Offspring develop at a more constant, favorable temperature
2. Offspring are protected
3. Offspring are portable–mothers are not tied to a nest

Disadvantage: Placenta is energetically expensive to produce, and bearing live young is energetically costly

Question 7

What are the evolutionary advantages of viviparity and placenta?

Answer 7

1. Offspring develop at a more constant, favorable temperature
2. Offspring are protected
3. Offspring are portable–mothers are not tied to a nest

Disadvantage: Placenta is energetically expensive to produce, and bearing live young is energetically costly

Question 8

What makes a primate a primate?

Answer 8

• Hands and feet that are efficient at grasping
• Flattened nails instead of claws on fingers and toes
• Relatively large brains
• color ivsion
• Complex social behavior
• Extensive parental care of offspring
• Forward-facing eyes

Question 9

What are the subgroups of primates?

Answer 9

Prosimians (“before-monkeys”) include:
Lemurs, tarsiers, pottos. Most are small-bodies, arboreal, and nocturnal.
Anthropoids (“human-like”) include:
- New world and old worl monkeys.
- Great apes, the hominidae

Monkeys are a phylogenetic grade

Question 10

What are hominids?

Answer 10

Great apes are also called hominids because they have relatively large bodies with long arms, short legsg, and no tail.

They also walk distinctly:
- Orangutans fist-walk on the ground. Gorillas knuckle-walk.
- Humans are the only living great ape that are fully bipedal walking on two legs.

Question 11

What are hominins?

Answer 11

Hominins are a monophyletic group comprising Homo Sapiens and more than 20 extinct. They are all bipedal.