Lecture 22 Flashcards
Organisms with no circulatory system
- Protozoans
- Porifera
- Cnidaria
- Ctenophora
- Platyhelminthes
- Nematoda
Organisms with open circulatory systems
- Most molluscs
- Arthropods
- Echinoderms
- Hemichordates
Organisms with closed circulatory systems
- Cephalopod molluscs
- Annelids
- Chordates
Vessels
- 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
Heart segments for different animals
- Fish
- Two chambers (1 atrium and 1 ventricle) • Single loop circulatory system
- Amphibians & most nonavian reptiles
- Three-chambers (2 atria, 1 ventricle)
- Double loop circulatory system
- Some mixing of de-oxygenated and oxygenated blood
- Crocodilians, Birds & Mammals
- four-chambers (2 atria, 2 ventricles)
- Double loop circulatory system
- Most efficient
r-selected reproduction
- short life expectancy
- Many offpring (thousands)
- Low % survival
- No parental care
- Cultural memes not passed down • no parental nourishment
K-selected reproduction
- Long life expectancy
- Few offspring
- High % survival
- Parental care
- Cultural memes passed down
- Nourish embryo
MOST r-selected and k- selected
MOST R •Bacteria • Molluscs • Insects • Fish • Amphibians • Reptiles • Mammals • Apes • Humans MOST K
Parthenogenesis
• development of embryo from unfertilized egg
Note: The egg is a sex cell!
• Referred to as an ‘incomplete form of sexual reproduction’
• Offpring are formed from gametes but only one parent contributes
genetic material
- Two types of parthenogenesis
- Haploid Parthenogenesis
- Diploid Parthenogenesis
Haploid Parthenogenesis (results in haploid offspring)
- Haploid ovum formed by meiosis
* Rare…occurs in some bees and nematodes
Diploid Parthenogenesis (results in diploid offspring):
- Case1: 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 parthenogeneis
- Offspring are clones of the parent
Reproduction in Fishes
• 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
General Patterns of Reproduction of fish
- Pelagic (open sea) marine teleosts
- e.g. Northern 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)
Sequential hermaphrodite – clown fish
- 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
Amazon molly reproduction
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
Reproduction in birds
• 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”
Egg Laying for birds
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
Mating Systems for birds
• Over 90% of avian species are monogamous
Two types of mating systems in animals:
• Monogamy: an individual has only one mate (theoretically!)
- Polygamy: an individual has more than one mate during breeding period
- Some birds mate for life,
- remain with partner throughout the year (e.g. geese, swans), or meet up each year in the breeding grounds or..
• Often both sexes participate in parental care
different from mammals where there is an unequal investment
Polygamy in birds (not common)
• Polygyny (many females, one male)
Females tend to choose the dominant male
• Polyandry (many males, one female)
Female will mate with several males, lays multiple clutches
Developmental State of Chicks
- Precocial
- Hatch covered with down
- Can run or swim as soon as they hatch
- Most can’t fly
- Fairly independent,
- Altricial
- Smaller eggs, less yolk (less investment)
- Hatch naked
- Unable to see or walk at hatch
- Remain in the nest for 1-2 weeks or more
- Must be fend constantly by parents
Reproduction in Mammals
• Defined mating seasons
- 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 of birth is favourable
- Male mammals fertile at any time; Timing of female fertility is restricted by the estrous cycle
Estrous Cycle
Estrous = period of heat of a female mammal associated with ovulation
• Monoestrous: single estrus during breeding season • E.g. dogs, foxes, bats
• Polyestrous: recurrence of estrus during breeding season• E.g. field mice. Squirrels
• 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
Reproductive Patterns In mammals
Monotremes
• Large, yolky eggs
• Earliest mammals laid eggs, and monotremes have retained this characteristic
- Marsupials
- Embryos develop in mother’s uterus but do not implant
- Born at a premature stage; complete development outside of uterus
- Placental Mammals
- 94% of mammals are placental
- Embryo is nourished through the placenta in the uterus
Monotremes development
- 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 mother’s pouch (echidna)
- Hatch after 12 more days
- Drink milk produced by mother’s mammary glands
- No nipples, so monotreme young lap milk from fur on mother’s belly
Marsupials development
- 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
Placental Mammals development
• Viviparous
• Prolonged gestation
• Contrasts with marsupials
• Embryos remain in the uterus nourished by food supplied
by the placenta (formed from amniotic membranes)
• Gestation period generally increases with animal size and lifespan
Placenta
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 begins
• Placenta attaches embryo to mother’s uterine wall
• Air, food, and waste are transferred across the placenta
Like bird reproduction , mammals can be
- altricial (immature and helpless)
* precocial (mature and mobile)
