Animal reproduction Flashcards
Fission
Asexual reproduction in some invertebrates
Separation of parent into 2 or more individuals of about the same size
Budding
New individuals arise from outgrowths of existing ones
Hydra and other cnidarians
Fragmentation
Breaking of body into pieces followed by regeneration of lost body parts
Pieces develop into adults
Segmented worms
Parthenogenesis
Development of new individual from unfertilized egg
Rotifers
“Twofold” cost of sexual reproduction
Sexual females have half as many daughters as asexual females
Why sexual reproduction is an evolutionary advantage
Genetic recombination: increased variation of offspring, increased rate of adaptation, shuffling of genes and elimination of harmful genes from population
Ovulation definition
Release of mature eggs at the midpoint of a female cycle
Control of reproductive cycles
Most animals exhibit reproductive cycles related to changing seasons
Reproductive cycles are controlled by hormones and environmental cues
Asexual whiptail lizards
Parthenogenesis
Females switch sexual roles (mounting triggers release of egg)
Hermaphroditic reproduction
2 hermaphrodites can mate
Some can self-fertilize
External fertilization
Eggs shed by female are fertilized by sperm in external environment
Example: female frog secretes eggs into pond, and male frog secretes sperm into pond to fertilize them
Internal fertilization
Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
Requires behavioral interactions and compatible sexual organs
Critical timing: environmental cues, pheromones, and/or courtship behavior
Gonads
Organs that produce gametes via meiosis
Female external reproductive structures
Clitorus: arousal
Labia: protect opening into vagina
Ovaries
Female gonads Contain follicles (partially developed egg, oocyte, surrounded by support cells; produce estradiol prior to ovulation)
Oogenesis
Development of oocyte into ovum (egg)
Prolonged process
Ovulation steps
Egg cell is expelled from follicle
Remaining follicular tissue forms into corpus luteum
Cilia in oviduct (fallopian tube) transport egg cell to uterus
Uterus lining (endometrium) contains many blood vessels
Corpus luteum
Follicule tissue minus egg cell
Secretes estradiol and progesterone that helps to maintain pregnancy
If egg isn’t fertilized, this degenerates