Deck 29: Reproduction and Development

Question 1

Is the fertility of a woman affected by the length of a given menstrual cycle or whether the cycles are regular or irregular? Explain.

Answer 1

Menstrual cycle is the cyclic preparation of the uterus to receive a fertilized egg for further development. This cycle is under hormonal control. The hormones that helps in the cyclic process are estrogen, follicle stimulating hormone, gonadotropin releasing hormone, etc.This cycle varies from individual to individual but the average period is of 28 days. Early or delayed cycle indicates no ovulation or irregular ovulation. The fertility of women depends on the regularity of the ovulation. In each cycle one egg matures to be fertilized. Thus the length or irregular cycles affect the fertility of a woman.

Question 2

The cnidarian, Hydra, reproduces

A) only sexually.
B) asexually.
C) by budding.
D) by fragmentation.
E) by both b and c.

Answer 2

Sexual reproduction is the process of giving birth to new ones by the union of gametes of two parents with opposite sex. This union of gametes causes genetic variation and helps in the process of evolution.
Hence option a is not the correct answer.
Asexual reproduction is the process of reproduction without the union of gametes. The new individuals are exact copies of their parents. There is no genetic variation and hence they evolve less. This is common in lower invertebrates like protozoa, sponges, jellyfish, etc. the different types of asexual reproduction are- fission, budding and fragmentation.
Hence option b is not the correct answer.
Fragmentation is the process where a new organism grows from a lost part of an existing organism. This is similar to regeneration. This is common in cnidarians, platyhelminths, echinoderms, etc.Hence option d is not the correct answer.
In budding, certain cells divide and develop on the body surface as buds. These buds proliferate and develops into a new animal after breaking away from the parent animal. Hydra performs this type of reproduction.
Hence option c is the correct answer.

Question 3

Those species that reproduce asexually tend to evolve very slowly, because all offspring of any one individual are alike, providing less genetic diversity for evolutionary selection. One advantage to asexual reproduction is that a constant combination of genes matches a stable, unchanging environment in which the animal lives. One disadvantage is that genetic diversity does not occur and a single environmental event may devastate an entire species.
Does parthenogenesis occur among vertebrates? If so, give an example.

Answer 3

Parthenogenesis is a type of asexual reproduction where a mature egg undergoes spontaneous activation and division to produce an offspring. There is no fertilization of the egg by the sperm. These offsprings have less adaptation to the environment in which they live.Parthenogenesis occurs in both vertebrates and invertebrates but relatively rare. The examples of parthenogenesis in vertebrates is the komodo dragon and the hammerhead shark. In both these animals, offsprings were produced even though the females were kept separate from the males. These offsprings are called as parthenogenetic animals.

Question 4

Looking at a variety of animals, what are the advantages to restricting reproduction to a limited time period? Why do so many animals have a sharply defined reproductive season during the year?

Question 5

Asexual reproduction is common in

A) the protozoa.
B) sponges.
C) jellyfish.
D) flatworms.
E) all of the above (a-d).

Question 6

In invertebrates, sexual reproduction involves the fusion of gametes from different individuals of a species. Thus, each offspring has a unique combination of genes inherited from two parents. Broadcast spawning simply involves the release of gametes into the water in which the invertebrate lives (e.g., sponges and corals).
What are the different types of hermaphroditism?

Question 7

In most sexual species, males produce far more gametes than do females. Why does this occur when, in most cases, only one male gamete can fertilize one female gamete?

Question 8

Broadcast spawning is an example of internal fertilization.

Question 9

Most female mammals have an estrus cycle. In an estrus cycle, hormones control the fertility period in order for the young to be born when environmental conditions are most favorable. One common reproductive strategy found in reptiles, birds, and mammals is shelled, desiccation-resistant eggs.
Why do you think amphibians and many fishes have external fertilization, whereas lizards, birds, and mammals rely on internal fertilization?

Question 10

Why are the accessory glands of the male so important in reproduction?

Question 11

In protandry, an animal is a male during its early life history and a female later in the life history.

Question 12

Most fishes and amphibians release eggs and sperm into the water, where the gametes unite by chance. Very few fertilized eggs grow to maturity. Nonavian reptiles and birds have internal fertilization and their embryos develop in a fluid-filled cavity surrounded by membranes and a shell to prevent desiccation. Mammals generally do not lay eggs, but give birth to their young. They are also amniotic, but most species are viviparous. Most mammals have an estrus cycle, but primates have a menstrual cycle.
Is there an advantage to internal fertilization? If so, describe this advantage.

Question 13

Why doesn't a women menstruate while she is pregnant?

Question 14

The three basic embryonic membranes that characterize the mammalian embryo are also found in

A) fishes.
B) amphibians.
C) reptiles.
D) birds.
E) Both c and d are correct.

Question 15

Semen consists of sperm from the testes and fluid from the seminal vesicles and prostate gland. Sexual stimulation causes erection of the penis and continued stimulation leads to ejaculation of semen. The production of sperm and secretion of testosterone from the testes is controlled by FSH and LH from the anterior pituitary gland.
Would natural selection favor those males that produce more sperm over those males that produce fewer sperm? Explain your answer.

Question 16

Which of the following structures is the site of spermatogenesis?

A) Prostate
B) Bulbourethral gland
C) Urethra
D) Seminiferous tubule
E) Both a and b

Question 17

At puberty, some oocytes are triggered by FSH to develop with each menstrual cycle.During the follicular phase, one follicle matures; ovulation is is the release of the follicle's secondary oocyte triggered by LH. This secondary oocyte only completes its division if fertilization occurs. During the luteal phase, the development of an additional oocyte is inhibited. If fertilization does not occur, the endometrium is sloughed off as menstrual bleeding. The four phases that occur in mammals with an estrus cycle are proestrus, estrus, metestrus, and diestrus.
How are the functions of FSH and LH similar in human male and females? How do they differ?

Question 18

FSH and LH are produced by the

A) ovaries.
B) testes.
C) anterior pituitary gland.
D) adrenal glands.

Question 19

One of the most critical stages of development occurs during the first trimester of a human pregnancy. Organogenesis begins during the fourth week. During the subsequent six months, growth and maturation occur. The placenta functions as an exchange site for nutrients and gases and is also a hormone producer.
In the absence of a pregnancy, what would be the expected effects of high levels of estrogen and progesterone in the human female?