Chapter 43: Animal Reproduction

What are advantages of asexual reproduction?

one individual can produce many clones quickly, favored in stable/predictable environments, used for colonizing new habitats without needing mate

What are the advantages of sexual reproduction?

increases genetic diversity, favored in unstable/unpredictable environments, variation improves chances of survival

What is binary fission?

organism splits into two equally sized organisms; some invertebrates like corals and anemones

What is budding?

adult produces outgrowth that separates and grows into new organisms; some invertebrates like hydra

What is fragmentation?

part of adult breaks off and regenerates into new organism; sea stars, flatworms, poriferans (sponges)

What is parthenogenesis?

in females, two eggs fuse without fertilization to produce offspring; invertebrates like water fleas, bees, daphnia; vertebrates like reptiles, amphibians, fish

How is sex determined in mammals?

XX - female

XY - male (Y)

How is sex determined in birds?

ZZ = male

ZW = female (W)

also in fish, insects, reptiles

What is temperature-dependent sex determination (TSD)?

sex determined by environmental temperature

Turtles—cooler = male, warmer = female

Alligators/crocodiles—warmer = male, cooler = female

What is sex change in animals?

some animals change sex during life

protogyny - female first

protandry - male first

in fish and oysters

What is haplodiploid sex determination?

haploid = male

diploid = female

in hymenoptera (bees, ants, wasps)

What does monoecious mean in sexual reproduction?

one individual has both male and female reproductive parts and can self-fertilize or mate with others; worms, slugs, snails

What is external fertilization?

females and males release eggs and sperm into water at same time to fertilize externally, mostly in aquatic environments; low survival rate

What is broadcast spawning?

all males and females release gametes simultaneously, triggered by time of year/day, leading to high genetic diversity

What is courtship spawning?

one male and one female release gametes together after courtship behavior; produces many offspring but low survival rate

What is internal fertilization?

male sperm is deposited inside female to fertilize eggs, protecting embryo from predation and drying out

What are the advantages of internal fertilization?

produces fewer offspring but higher survival rate

What is viviparous reproduction?

embryo attaches to mother's oviduct and obtains nutrients directly from her; live birth; most mammals

What is oviparous reproduction?

fertilized eggs are laid outside mother's body; embryos get nutrition from egg yolk; fish, reptiles, birds

What is ovoviviparous reproduction?

fertilized eggs develop inside mother, hatch in utero, born alive; nutrition from egg yolk; sharks, snakes, lizards

What unusual behavior occurs in some ovoviviparous sharks?

young obtain nutrition by cannibalizing siblings inside the mother

What is spermatogenesis?

production of sperm

What are spermatogonia?

cells in the testes that undergo mitosis and produce primary spermatocytes

What happens when a spermatogonium divides by mitosis?

produces diploid cells: spermatogonium, primary spermatocyte (produces sperm via meiosis)

What happens to primary spermatocytes during spermatogenesis?

undergoes meiosis I to produce two secondary spermatocytes

What happens after meiosis II in spermatogenesis?

each secondary spermatocyte divides into two spermatids, totaling four spermatids

How do spermatids become sperm?

differentiate into mature sperm cells in lumen of seminiferous tubules

When do spermatogonia become active?

inactive at birth, activated during puberty by hormones from anterior pituitary

What is oogenesis?

Egg production

What are oogonia?

cells in ovaries that divide by mitosis to form 2 primary oocytes

What happens to primary oocytes before birth?

begin meiosis but stop at Prophase I; females are born with all eggs arrested at this stage

What triggers primary oocytes to resume meiosis?

gonadotropic hormone from anterior pituitary and follicle-stimulating hormone during puberty

What results from completion of meiosis I in oogenesis?

two haploid cells: larger secondary oocyte arrested in metaphase II, smaller polar body

When is the secondary oocyte released in oogenesis?

during ovulation

What happens if the secondary oocyte is fertilized?

completes meiosis II, producing zygote and second polar body that degenerates