Ch 46 Animal Reproduction Flashcards Preview

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Flashcards in Ch 46 Animal Reproduction Deck (78):
1

Sexual reproduction

The creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote

2

Asexual reproduction

The creation of offspring without the fusion of egg and sperm

3

How do many invertebrates reproduce asexually?

Fission

4

Fission

Separation of a parent into two or more individuals of about the same size

Form of asexual reproduction

5

Budding

New individuals arise from outgrowths of existing ones

Form of asexual reproduction

6

Fragmentation

Breaking of the body into pieces, some or all of which develop into adults

Form of asexual reproduction

7

Parthenogenesis

The development of a new individual from an unfertilized egg

8

In what organisms does parthenogenesis occur?

1) In many plants

2) Some invertebrates

3) Some vertebrates (amphibians and reptiles)

9

What is one example of parthenogenesis occurring in vertebrate?

Aspidoscelis (whiptail lizards)

10

In how many species of Aspidoscelis does parthenogenesis occur?

15

11

How did the species of Aspidoscelis that reproduce by parthenogenesis arise?

From hybridization among sexual species

12

What is the "twofold cost" of sexual reproduction?

Sexual females have half as many daughters as asexual females

13

Do most eukaryotic species reproduce sexually or asexually?

Sexually

14

Why does sexual reproduction provide potential advantages over asexual reproduction?

It results in genetic recombination

15

Potential advantages of sexual reproduction

1) Increases the variation in offspring, providing an increase in the reproductive success in changing environments

2) Increases the rate of adaptation

3) Shuffles the genes and eliminates harmful genes from a population

16

Most animals exhibit reproductive cycles related to what?

Changing seasons

17

Most animals exhibit reproductive cycles controlled by what two things?

1) Hormones

2) Environmental cues

18

Ovulation

The release of mature eggs at the midpoint of a female cycle

19

Are reproductive cycles and mating behaviors retained in asexual whiptail lizards (Aspidoscelis)?

Yes

20

Gonads

The organs that produce gametes

21

In addition to gonads, many animals possess what?

Accessory organs

Involved in the transfer and reception of sperm

22

Spermatheca

Organ in many female insects where sperm is stored during copulation

23

Cloaca

A common opening for digestive, excretory, and reproductive systems

Typically found in nonmammalian vertebrates

24

Female external reproductive structures of humans

1) Sensory clitoris

2) Two sets of labia

25

Female internal reproductive structures of humans

1) Pair of gonads

2) System of ducts and chambers that carry gametes and house the embryo and fetus

26

Male external reproductive structures of humans

1) Penis

2) Scrotum

27

Male internal reproductive structures of humans

1) Gonads

2) Accessory glands

28

Vagina

Thin-walled chamber that is the repository for sperm during copulation

Serves as birth canal

29

Each ovary contains many what?

Follicles

30

Follicle

Contains an oocyte

31

Oocyte

A partially developed egg

32

Ovum

A fully developed egg

33

Oogenesis

Process where an oocyte develops into an ovum

34

Oviduct (fallopian tube)

Tube through which the ovum cell travels from the ovary to the uterus

35

Endometrium

Uterus lining

36

How does the endometrium support egg development?

It has many blood vessels

37

Seminiferous tubules

Site of sperm formation

Found in the testes

38

Leydig cells

Produce hormones

Scattered between the tubules

39

Sperm passes from the testes to what?

The epididymis

40

During ejaculation, sperm is propelled through what two structures?

1) Vas deferens

2) Ejaculatory duct

41

Urthera

Structure through which sperm exits the penis

42

The human penis is composed of what?

Three cylinders of spongy erectile tissue

43

What causes an erection?

During arousal, the erectile tissue fills with blood from the arteries

44

Semen

Composed of sperm and secretions from three sets of accessory glands

45

Three accessory glands that help form semen

1) Two seminal vesicles

2) Prostate gland

3) Bulbourethral glands

46

Seminal vesicles

Contribute ~60% of the total volume of semen

47

Prostate gland

Secrets its products directly into the urethra through several small ducts

48

Bulbourethral glands

Secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra

49

Spermatogenesis

The development of sperm

50

How many sperm are produced each day?

Millions

51

How long does it take each sperm to develop?

7 weeks

52

Oogenesis

The development of an egg

53

Ovulation

The monthly release of a mature egg

54

How many of the products of meiosis develop into sperm?

All four

55

How many of the products of meiosis develop into an egg?

One of the four

56

What are the two main male reproductive hormones?

1) Follicle stimulating hormone (FSH)

2) Leutenizing hormone (LH)

57

Follicle stimulating hormone (FSH)

Promotes the activity of Sertoli cells

58

Sertoli cells

Nourish developing sperm

59

Leutenizing hormone (LH)

Regulates Leydig cells

60

Leydig cells

Secrete tetosterone and other androgens

61

Testosterone and other androgens promote what?

Spermatogenesis

62

What closely links the two cycles of female reproduction?

Hormones

63

Ovarian cycle

Female reproductive cycle defined by changes in the ovaries

64

Menstrual cycle (uterine cycle)

Female reproductive cycle defined by changes in the uterus

65

What happens to the endometrium before ovulation?

It thickens in preparation for embryo implantation

66

Menstruation

Shedding of the endometrium

Occurs if an embryo does not implant into the endometrium

67

What three hormones stimulate follicle growth?

1) Follicle stimulating hormone (LSH)

2) Leutenizing hormone (LH)

3) Gonadotropin releasing hormone (GnRH)

68

Follicle growth and an increase in the hormone estradiol leads to what?

Ovulation and the release of a secondary oocyte (mature egg)

69

Where do immature eggs form?

The female embryo

70

When do eggs complete their development?

Many years after birth

71

What does the follicle become after releasing an egg?

The corpus luteum

72

The corpus luteum secretes what two hormones to maintain pregnancy?

1) Estradiol

2) Progesterone

73

Human chorionic gonadotropin (hCG)

Hormone released by the embryo to prevent menstruation

74

How does the embryo obtain nutrients for the first 2 to 4 weeks?

Directly from the endometrium

75

What forms the placenta?

Mingling between the trophoblast and endometrium

76

What is one of the few examples of positive feedback loops in humans?

Hormonal controls in birth

77

What replaces the menstrual cycle in most animals?

Estrous cycle

78

Estrous cycle characteristics

1) Endometrium is reabsorbed by the uterus

2) Sexual receptivity is limited to a "heat" period

3) Length and frequency of the estrous cycles vary from species to species