Circulation & Reproduction

Question 1

Explain the circulatory system

Answer 1

Mammals require circulatory system to work over large distances - high metabolic demands

Question 2

What are the 3 components to the circulatory system?

Answer 2

- Fluid 
   Blood or hemolymph
- Pump
   Heart 
- Vessels 
    Vascular components: arteries, veins, capillaries

Question 3

What are vessels?

Answer 3

• Two types of vessels in the cardiovascular system
  Oxygenated blood leaves heart through arteries
  Deoxygenated blood returns to heart through veins
• Gases are exchanged across thin walled capillaries

Question 4

What about the pump?

Answer 4

• Heart is segmented (Number of chambers differs among taxa)
• Fish
  2 chambers (1 atrium and 1 ventricle)
  Single ;loop circulatory system
• Amphibians & most nonavian reptiles
  3 chambers (2 atria and 1 ventricle)
  Double loop circulatory system
  Some mixing of deoxygenated and oxygenated blood
• Crocodiles, Birds & Mammals
  4 chambers (2 atria, 2 ventricles)
  Double loop circulatory system
  Most efficient

Question 5

What are the 2 opposing strategies for reproduction?

Answer 5

r-selected reproduction

k-selected reproduction

Question 6

What is r-selected reproduction?

Answer 6

• Short life expectancy
• Many offspring (thousands)
  Low % survival
• No parental care
  Cultural memes not passed down
  No parental nourishment

Question 7

What is k-selected reproduction?

Answer 7

• Long life expectancy
• Few offspring
  High % survival
• Parental care
  Cultural memes passed down
  Nourish embryo

Question 8

Most r-selected to most k-selected

Answer 8

Bacteria 
Molluscs
Insects
Fish 
Amphibians
Reptiles
Mammals
Apes 
Human

Question 9

What are their types of sexual reproduction?

Answer 9

• Bisexual Reproduction
  Most common form
  Male and female gametes (sperm or egg) are produced
  Two haploid (n) gametes combine to form a zygote (2n)
• Hermaphroditism
  Male and female organs occur in sam individual
  Most avoid self fertilization
• Parthenogenesis (can also be categorized as asexual)
  Embryo develops from unfertilized egg (sperm may activate but not fuse with egg)

Question 10

What are the types of hermaphroditism?

Answer 10

• Simultaneous
  Active female and male organ at the same time
• Sequential
  Active sex changes at some point during life

Question 11

Explain in more detail parthenogenesis

Answer 11

• Development of embryo from unfertilized egg
• Referred to as an incomplete form of sexual reproduction
  Offspring are formed from gametes but only one parent contributes genetic material
• Two types
  Haploid
  Diploid

Question 12

What is haploid parthenogenesis?

Answer 12

• Haploid ovum formed by meiosis

- Rare occurs in some bees and nematodes

Question 13

What is diploid parthenogenesis (results in diploid offspring)?

Answer 13

Case 1: meiosis occurs but diploid condition is restored

• Chromosomal duplication
• Autogamy (rejoining of haploid nuclei)
• Offspring are not clones of parent (recombination occurs)

Case 2: no meiosis occurs

• This is considered an asexual form of parthenogenesis
• Offspring are clones of the parent

Question 14

How is reproduction done in fishes?

Answer 14

• Mostly dioecious, external fertilization, oviparous
  Also instances of: monoecious, internal fertilization, ovoviviparous, viviparous
• Often release vast numbers of gametes
  e.g large female cod will release 4-6 million eggs in a single spawning
  This reproductive strategy is associated with lower parental investment in the offspring
• r selected reproduction

Question 15

What are the general patterns of reproduction in fish?

Answer 15

• Pelagic (open sea) marine teleosts
  e.g. Norther cod
  Minute, buoyant, transparent eggs
  Eggs hatch into larvae as they float in the ocean
• Near shore and benthic (bottom dwelling) fish
  Larger eggs, with more yolk
  Non buoyant, adhesive
  Eggs are buried, attached to vegetation, deposited in nests
  Many benthic fish guard their eggs (male)

Question 16

What is sequential hermaphrodite in clown fish?

Answer 16

• Live in social groups (in symbiosis with sea anemones)
• Group consists of a breeding pair (one male, one female) and a number of undifferentiated fish
• If the female dies, the adult male becomes female, and one of the smaller fish takes his place

Question 17

What is another unusual reproduction in fish?

Answer 17

• Amazon Molly (all female species)
• Egg is diploid when it is laid (no meiosis)
• Male sperm from a related species may be required to stimulate the egg
• Offspring are clones of the mother
• This is parthenogenesis

Question 18

How is the reproduction done in birds?

Answer 18

• Dioecious
• All oviparous
• Generally no external genitalia (some ducks have penises)
• Cloaca
  Opening to the reproductive system in males and females
  Opening for the intestinal and urinary tract
• Internal fertilization by cloacal kiss

Question 19

How do birds lay eggs?

Answer 19

• Female generally lays one egg per day until she has a full clutch
  Determinate layers: produce a certain number of eggs and stop
  Indeterminate layers: replace eggs if some are removed

Question 20

How is the mating system in birds?

Answer 20

• Over 90% of avian species are monogamous
• Two types of mating systems in animals
  Monogamy: an individual has only one mate
  Polygamy: an individual has more than one mate during breeding period
• Some birds mate for life
  Remain with partner throughout the year
  Meet up each year in the breeding grounds
• Often both sexes participate in parental care
  Different from mammals where there is an unequal investment

Question 21

What is polygyny in birds?

Answer 21

• E.g. sage grouse gather in a collective display ground
• Males defend individual territories and display
• Females tend to choose the dominant male

Question 22

What is polyandry in birds?

Answer 22

• E.g. spotted sandpiper
• Female will mate with several males
• She lays multiple clutches of eggs which individual males care for

Question 23

What are the developmental states of chicks?

Answer 23

Precocial

Altricial

Question 24

Explain precocial

Answer 24

• Hatch covered with down
• Can run or swim as soon as they hatch
• Most can’t fly
• Fairly independent, but still fed and protected from predators for some time

Question 25

Explain altricial

Answer 25

• Smaller eggs, less yolk (less investment)
• Hatch naked (no feathers)
• Unable to see or walk at hatch
• Remain in the nest for 1-2 weeks or more
• Must be fend constantly by parents

Question 26

How is reproduction in mammals?

Answer 26

• Defined mating seasons
  Winter or spring
  Timing of birth corresponds with warmer weather
• Delayed implantation lengthens the gestation period in some mammals
  Blastocyst doesn’t implant in the uterine wall immediately
  Gestation is extended so that the timing if birth is favourable
• Male mammals fertile at any time; Timing of female fertility is restricted by the estrous cycle

Question 27

What is the estrous cycle?

Answer 27

• Estrous = period of heat of a female mammals associated with ovulation
• Monoestrous: single estrus during breeding season
• Polyestrous: recurrence of estrus during breeding season
• Menstruation = discharge of blood and uterine endometrial tissue at the beginning of the menstrual cycle
  Most animals reabsorb the endometrial tissue
  Humans, chimps, elephant shrews and some bats discharge it

Question 28

What are the reproductive patterns in mammals?

Answer 28

Three different patterns of reproduction in mammals:

• Monotremes
• Marsupials
• Placental mammals

Question 29

What are monotremes?

Answer 29

• Large, yolky eggs
• Earliest mammals laid eggs, and monotremes have retained this characteristic
• Egg laying (oviparous) mammals
• All live in Australia or New Guinea
• Very small group: Platypus and 4 species of echidna
• Embryos develop in uterus for 10 to 12 days (nourished through yolk)
• Thin, leathery shell is secreted around the embryos
• Eggs laid in a burrow (platypus) or mothers pouch (echidna)
• Hatch after 12 more days
• Drink milk produced by mothers mammary glands
  No nipples, so monotreme young lap milk from fur on mothers belly

Question 30

What are marsupials?

Answer 30

• Embryos develop in mothers uterus but do not implant
• Born at a premature stage; complete development outside of uterus
• Viviparous mammals characterized by premature birth
• Most have specialized pouches where they continue to nurse and protect the young after birth
• Viviparous mammals (young are born premature)
• Transient placenta (yolk sac placenta)
• Gestation is short (young are tiny: effectively still embryos)
• Lactation and parental care is long
• Some (not all) have pouches

Question 31

What is the distribution of marsupials?

Answer 31

• Most found in Australia and New Guinea (approx. 200 species)
  Kangaroos, wallabies, wombats, koala, Tasmanian devil, possums
• Some found in the Americas (approx. 70 species)
  Opossums
  One North American species: Virginia Opossum

Question 32

What are the placental mammals?

Answer 32

• 94% of mammals are placental
• Embryo is nourished through the placenta in the uterus
• Viviparous
• Prolonged gestation
  Contrasts with marsupials
• Embryos remain in the uterus nourishment by food supplied by the placenta (formed from amniotic membranes)
• Gestation period generally increases with animal size and lifespan
  Elephant (22 months)
  Mouse (21 days)

Question 33

What is the placenta?

Answer 33

• Placenta is a modified amniotic egg
  Amnion surrounds embryo with amniotic fluid (as in other animals)
  Allantois, yolk sac, and part of chorion contribute to the placenta
  Chorion surrounds entire thing and breaks as labour breaks
• Placenta attaches embryo to mothers uterine wall
  Air, food, and waste are transferred across the placenta

Question 34

What is the developmental state at birth for mammals?

Answer 34

• Like birds, mammals can be
  Altricial (immature and helpless)
  Precocial (mature and mobile)