animal reproduction Flashcards
what is asexual reproduction of animals list the types
- features: one diploid parent, no fertilisation, no special reproductive organs or cells
- new individuals genetically identical to parent and to each other (clone), mitosis
- usually: vertebrates, lower order organisms, easily done / fast, colonisation = quick
- types: fragmentation, regeneration, budding and parthenogenesis
describe the types of asexual reproduction in animals
- fragmentation: breaking into many fragments that become a new animal (flatworms, decapitate and head will grow back), accompanied by regeneration, mitosis
- regeneration: of individual body parts, mitosis, process of renewal, restoration and growth, removal of a limb when being chased (predator eats limb)
- budding: new organism develops from outgrowth / bud due to cell division at a particular site, develop organs then detach (hydra) or remain attached, as a colony (coral)
- parthenogenesis: ‘virgin origin’, embryo develops from an unfertilised diploid egg (2n) (bees, ants, wasps, lizards, sharks in captivity)
what is a unisexual animal (parthenogenesis)
- all female species
- egg is produced by meiosis and needs to be activated for development (male behaviour)
- obligate parthenogenesis: females act like males and go through courtship behaviour to stimulate ovulation, evolved from sexual reproduction (no longer need males, still have hormones and gonads)
what are the advantages / disadvantages of asexual reproduction
A:
- rapid population growth
- successful coloniser
- population growth from isolated individuals
- no need to bring two parents together
- all female genes are passed to offspring, mostly females are produced = more eggs
D:
- no genetic recombination
- mitotic copies are identical
- little evolutionary flexibility
- limited capacity to shift gene combinations / adjust to sudden change in environment (exclude cyclical parthenogenesis)
- will reach population carrying capacity (death at same time, clones)
what is sexual reproduction of animals and list the different types
- formation of gametes (cells), gonads (organs), physiology
- new individuals produced through fusion of haploid gametes (ovum and sperm)
- A: fertilisation, meiosis, genetically different offspring
- D: more complicated and costly
- ovum: large, stored yolk, generally nonmotile, ovary
- sperm: small, motile, more numerous, made in testis
- hermaphroditism, gametogenesis, indirect / direct development, gametogenesis, oviparous, viviparous, ovoviviparous
what is hermaphroditism (sexual)
- produce both male and female gametes
- avoid self-fertilisation: prefer to exchange gametes with other members of same species, receive or donate sperm, cross fertilisation (like cross pollination)
monoecious: - protandry: male to female, large female has greater reproductive success as it can produce more eggs
- protogyny: female to male, large male will protect the harem; one male, multiple females
wrasse (protogyny): when only male in harem dies largest female becomes male, change colour, shape
what is gametogenesis (sexual)
- spermato / oo genesis
- production of gametes by germ cells in gonads (testes / ovaries)
- released through gonoducts (vas deferens / oviduct)
- during embryogenesis germ cells migrate to gonads
- oogonia (2n) and spermatogonia (2n)
undergo repeated miotic divisions to produce haploid cells (n), ova and sperm
describe the different structures of an egg
- harsher environment = more layers
- terrestrial: shell (protection), yolk (nutrition), outer and inner shell membrane, vitelline membrane (thicker)
aquatic: no shell, jelly coat, vitelline membrane (thinner)
describe internal and external fertilisation (sexual)
E:
- external to body, eggs shed by female are fertilised by sperm in external environment (close proximity)
- parents don’t require physical contact (deposit near one another)
- enormous number of gametes released (chance)
- aqueous environment, tend to have no parental care (no certainty of paternity)
I:
- sperm deposited in or near female reproductive tract
- fewer gametes but higher survival rate
- protection of embryos and parental care of young
- terrestrial environment, placental mammals, gestation period
describe the stages of embryonic development
- plant = formation of cotyledon, animals = more complex
cleavage: - rapid cell division, follows predictable pattern
- cells reduce in size (zygote stays same size)
- ends at blastula; blastomere (hollow ball of cells) or blastocoel (fluid filled cavity)
gastrulation: - development of basic features, germ layers
- ectoderm: outer layer, outer body covering / NS
- mesoderm: intermediate layer, tissues and organs
- endoderm: inner layer, lining of gut and organs
- archenteron: cavity, primitive gut
- blastopore: first opening for primitive gut (anus or mouth, humans = anus)
organogenesis: - formation of organs from tissues, neurulation / limb formation
what is indirect development (sexual)
- metamorphoses: intermediate larval stages
- different stages of young (inhabiting different niche)
- advantages: many eggs produced (small amount of yolk, cheap to make), wide dispersal (niche), low investment, high output, independent, less competition of own family
- disadvantages: high mortality
what is direct development (sexual)
- parents are internal fertilisers, offspring resembling miniature adults
- advantages: low mortality, high investment, low output, high survival, mammals nourish via placenta (lactation period)
- disadvantages: very few eggs, very yolky eggs, costly to make, no dispersal (with parents forever)
what is oviparous
- egg laying, development occurs outside mother (fish, amphibians, reptiles, birds)
- advantages: less energy, developing embryo = nutrients within yolk, more eggs
- disadvantages: lack of parental investment reduces likelihood of survival
what is viviparous
- live birth, placental connection (mammals and marsupials)
- advantages: higher parental investment, high survival
- disadvantages: energy-expensive, low number of offspring
what is ovoviviparous
- embryos develop in eggs, remain inside mother (invertebrates, some fish / reptiles)
- advantage / disadvantage: protection, intermediate amount of energy, intermediate amount of offspring, intermediate survival probability on average
