Animal Reproduction Flashcards

Offspring is a combination of 2 parents

Offspring is from 1 parent

Asexual Favored--1. no males2. environment is stable
Sexual Favored--1. mates available2. changing environment

:Production of male and female gametes
Spermatogenesis- formation of sperm- spermatogonia(stem cells 2N) divide by mitosis -divide by meiosis to form 4 spermatocytes (N)-develop into spermatozoian (get tails) (mature sperm cells N)
- 4 sperm from 1 cell
Oogenesis- formation of eggs-oogonia (2N) divide by meiosis to create three polar bodies and 1 Oocyte (N) (happens when still fetus)-Oocyte develops into the ovum (mature egg cell N)-Only considered ovum when punctured by sperm
-1 egg (three polar bodies)

Echidna, platypus-- eggs

1. kangaroos, etc. -- partly developed live-born2. other

Sexual Cannibalism-females can mate with multiple males-male is very small compared to female-male will come up and start to mate with the female by sticking its penis in a hole by the mouth of the female spider-If male wants to father more offspring...-he does an elaborate backflip as he is inseminating her and allows himself to be eaten by her -distracts her for awhile allowing for his sperm to fertilize more eggs

-One snail impales neck of the other snail with a "love sword"-when one nail is darted it stimulates it to lay eggs

-Masculinized females --- long penis like clitoris through which baby must be born --- male shows submission ---- female clitoris rolls up exposing a hole --- penis has to get in hole --- when giving birth it often rips apart and takes weeks to heal

--elaborate dance in the water--female lays eggs in water--male smashes eggs into back of female--she carries them in her skin pouch as they develop--little froglets pop out her back

Sea stars, sea urchins, most insects, birds, reptiles, amphibians, snakes

Most mammals-some fish, amphibians, reptiles and invertebrates

Natural selection favors live birth especially in cold habitats-low temperatures slow the development of embryos so in cold it might be advantageous for females to retain eggs inside their bodies so that the offspring can develop at a more favorable temperature.

-The fetus crawls out of the vagina after a couple of weeks-crawls into the pouch and latches onto nipple to develop-As this happens, an egg descends into the uterus
Advantageous----can have another offspring more quickly- can have 3 offspring at any given time
--time released from mother is earlier--have a lot of offspring relative to time

Mothers carry offspring for relatively long periods of development during gestation and nourish them via a placenta
--placenta has a high surface area