Vertebrates 5

Question 1

3 unique features to mammals

Answer 1

-Hair (used for insulation, camouflage, sensory and defence)
-Mammary Glands (milk production)
-Sweat glands

Question 2

what is a synapsid?

Answer 2

• Mammals evolved from synapsids
  -Synapsids are characterized by a hole in their skull

Question 3

Early Mammals

Answer 3

-Small, arboreal, shrew-like insectivores
-“improvements” to the middle ear bone (evolved from gills which then became the jaw)

Question 4

When did mammals become popular?

Answer 4

-Mammals did not radiate until the extinction of dinosaurs
-When dinosaurs went extinct mammals filled empty terrestrial and marine niches
-Returned to the oceans(amphibians had come out)

Question 5

How do we know mammals used to be massive?

Answer 5

Due to la brea tar pits in LA that would cause the massive mammals to get stuck. A lot of their fossils can be found there

Question 6

What caused the extinction of large mammals?

Answer 6

-Humans setting fires
-Climate change

Question 7

Characteristics of mammals

Answer 7

• 4 chambered heart
• Endotherms
  -Internal fertilization
  -Specialization in teeth among species(varied diets)(heterodonty)

Question 8

What are the three mammalian groups?

Answer 8

1. Porotherians
   2.Echidna
   3.Eutherians

Question 9

Characteristic of Porotherians (example)

Answer 9

-Egg laying(lay shelled eggs)
-Egg incubation until hatching
-No placenta
-Fertilize internally
-Nourish egg outside the mother, parents incubate the egg
-Have mammary glands(no nipples, young suck the fur)
Ex. Platypus

Question 10

Characteristics of Echidnas (example)

Answer 10

-Short gestational period(have a placenta)
-Fetus complete development in pouch
-Pouched
-Viviparous(give birth to live young)
-Do not lay eggs
-Newborns crawl over their mother body to the pouch(then attach to the nipple)
Example: Kangaroo

Question 11

Characteristics of eutherians(example)

Answer 11

-Viviparous
-Do not lay eggs
-Placental mammals, embryo/amniotic egg retained in female reproductive tract and nourished by placenta

Question 12

What is convergent evolution?

Answer 12

An evolutionary process in which completely unrelated organisms evolve structures, traits or morphological features that have the same function

Question 13

What is the placenta? How is it formed? What is its function?

Answer 13

-An organ formed by the embryo and mother after implantation
-Formed by extra embryonic membranes and uterine lining
-Site of gas and nutrient exchange between mother and embryo
-Produces hormones necessary to maintain pregnancy

Question 14

How does the placenta work?

Answer 14

-Substances pass from mother to embryo via diffusion
-No blood or plasma mixing
-Two separate blood systems

Question 15

What molecules move across the placenta?

Answer 15

-Drugs, Alcohol
-Urea
-Nutrients(vitamin, sugars)
-O2 and CO2 (fetal hemoglobin has a higher affinity for oxygen therefore it diffuses from the mother)
-Hormones