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Flashcards in Animal reproduction Deck (47):
1

Fission

Asexual reproduction in some invertebrates
Separation of parent into 2 or more individuals of about the same size

2

Budding

New individuals arise from outgrowths of existing ones
Hydra and other cnidarians

3

Fragmentation

Breaking of body into pieces followed by regeneration of lost body parts
Pieces develop into adults
Segmented worms

4

Parthenogenesis

Development of new individual from unfertilized egg
Rotifers

5

"Twofold" cost of sexual reproduction

Sexual females have half as many daughters as asexual females

6

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

7

Ovulation definition

Release of mature eggs at the midpoint of a female cycle

8

Control of reproductive cycles

Most animals exhibit reproductive cycles related to changing seasons
Reproductive cycles are controlled by hormones and environmental cues

9

Asexual whiptail lizards

Parthenogenesis
Females switch sexual roles (mounting triggers release of egg)

10

Hermaphroditic reproduction

2 hermaphrodites can mate
Some can self-fertilize

11

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

12

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

13

Gonads

Organs that produce gametes via meiosis

14

Female external reproductive structures

Clitorus: arousal
Labia: protect opening into vagina

15

Ovaries

Female gonads
Contain follicles (partially developed egg, oocyte, surrounded by support cells; produce estradiol prior to ovulation)

16

Oogenesis

Development of oocyte into ovum (egg)
Prolonged process

17

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

18

Corpus luteum

Follicule tissue minus egg cell
Secretes estradiol and progesterone that helps to maintain pregnancy
If egg isn't fertilized, this degenerates

19

Female reproductive opening

Uterus narrows at cervix, then opens into vagina
Vagina opens to outside
Vagina serves as repository for sperm and the birth canal

20

Male external and internal reproductive organs

External: scrotum and penis
Internal: gonads and accessory glands

21

Testes

Male gonads
Consist of highly coiled tubes surrounded by connective tissue

22

Seminiferous tubules

Coiled tubes in testes
Site of sperm formation

23

Leydig cells

Produce hormones and are scattered between seminiferous tubules

24

Scrotum

Outer covering of testes
Outside abdominal cavity: temperature is low enough to produce sperm

25

Sperm flow in ejaculation

Seminiferous tubules -> epididymus (coiled tubules outside of testes) -> vas deferens (muscular tube) -> ejaculatory duct -> urethra

26

Semen

Sperm + secretions from accessory glands

27

Seminal vesicles

Contribute about 60% of total volume of semen
Male accessory gland

28

Prostate gland

Secretes anticoagulant enzymes and sperm nutrients directly into urethra through several small ducts
Male accessory gland

29

Penis

Composed of 3 cylinders of spongy erectile tissue
During arousal, erectile tissue fills with blood from arteries, causing erection

30

Spermatogenesis

Development of sperm
Continuous and prolific (millions of sperm are produced each day, and each sperm takes about 7 weeks to develop)

31

3 ways spermatogenesis differs from oogenesis

1. All 4 products of meiosis develop into sperm, while only 1 of 4 develop into egg
2. Spermatogenesis occurs throughout adolescence and adulthood
3. Sperm are produced continuously without prolonged interruptions as in oogenesis

32

Spermatogenesis steps

Primordial germ cell in embryo ->
Mitosis ->
Spermatogonial stem cell ->
Mitosis ->
Spermatogonium ->
Mitosis ->
Primary spermatocyte ->
Meiosis I ->
Secondary spermatocyte ->
Meiosis II ->
Early spermatid ->
Differentiation ->
Sperm cells

33

Sertoli cells

Provide nutrients to developing sperm (spermatids) in spermatogenesis

34

3 parts of sperm cell

Head: fertilizes egg
Midpiece
Tail

35

Sperm head components

Acrosome: vacuole that contains enzymes to eat through egg
Nucleus: contains haploid genome

36

Sperm midpiece

Contains many mitochondria: generate ATP to "swim"

37

Oogenesis steps

Primordial germ cell in embryo ->
Mitosis ->
Oogonium ->
Mitosis ->
Primary oocyte (present at birth; arrested in prophase of meiosis I) ->
Completion of meiosis I and onset of meiosis II (occurs at puberty) ->
Secondary oocyte (arrested at metaphase of meiosis II) ->
Ovulation and sperm entry ->
Completion of meiosis II ->
Fertilized egg

38

Gonadotropin-releasing hormone (GnRH)

Secreted by hypothalamus (part of brain that regulates reproduction): stimulated by high levels of estradiol in females and inhibited by high levels of testosterone in males
Directs release of follicle stimulating hormone (FSH) and lutenizing hormone (LH) by anterior pituitary gland

39

Menstrual cycle

Menstrual flow phase (day 0 to day 5): FSH and LH stimulate follicle to grow, low estradiol and progesterone cause release of endometrium
Proliferative phase (day 6 to day 14): follicle matures, increase in estradiol causes spike in LH, LH triggers release of egg cell
Secretory phase (day 15 to day 28): corpus luteum forms and secretes estradiol and progesterone, which cause thickening of endometrium
After day 28, cycle repeats

40

Estrous cycles

Characteristic of most mammals (except primates and humans)
Endometrium is absorbed by uterus
Sexual receptivity is limited to a "heat" period

41

Hormonal control of male reproductive system

Hypothalamus secretes GnRH
GnRH activates anterior pituitary gland, which releases FSH and LH
FSH stimulates sertoli cells, which stimulate inhibin (inhibit anterior pituitary from producing FSH) and spermatogenesis
LH stimulates Leydig cells, which stimulate testosterone (inhibits hypothalamus and anterior pituitary), which stimulates spermatogenesis
Hormone levels are steady, except for morning

42

Vasectomy

Ties off vas deferens

43

Birth control

Prevent oocyte development and ovulation
No sloughing of endometrial lining

44

Condom or abstinence

Prevent entry of sperm into vagina

45

Spermicides or diaphragm (inserted into vagina)

Prevent sperm movement through female reproductive tract

46

Morning-after pill

Prevent union of sperm and egg and implantation of blastocyst in endometrium

47

Tubal ligation

Ties off oviducts