lecture 27

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Questions and Answers

What happens to the oocyte after fertilization?

It undergoes changes that prevent polyspermy (correct)

It starts to form a blastula

It begins to form a morula

It begins to divide by meiosis

What is the primary function of gametogenesis?

Formation of gametes (correct)

Formation of tissues

Formation of somatic cells

Formation of organs

During what stage of development does the embryo grow into a fetus?

During the third trimester

Towards the end of the first trimester (correct)

During the first trimester

During the second trimester

What is the process by which the three germ layers are formed?

Gastrulation Signup and view all the answers

What is the result of capacitation in sperm?

Increase in motility Signup and view all the answers

What is the term for the process of fertilization by more than one sperm?

Polyspermy Signup and view all the answers

What is one of the main reasons why asexual reproduction is not ubiquitous?

Beneficial mutations can be spread through the population via sex Signup and view all the answers

What is the main difference between aquatic and terrestrial vertebrate reproduction?

External fertilization is used in aquatic vertebrates, while internal fertilization is used in terrestrial vertebrates Signup and view all the answers

What is the function of the acrosome in male gametes?

To contain enzymes that can penetrate the outer coating of the egg Signup and view all the answers

What is the result of a decrease in estradiol and progesterone from the ovaries in women?

Menopause Signup and view all the answers

What is the main difference between r-strategists and k-strategists?

Number of offspring vs parental investment Signup and view all the answers

What is the function of the hypothalamus in the reproductive system?

To release gonadotropin-releasing hormone Signup and view all the answers

What process reduces the number of chromosomes in gametes during sexual reproduction?

Meiosis Signup and view all the answers

What is the result of the fusion of gametes during sexual reproduction?

A zygote Signup and view all the answers

What type of reproduction involves the production of clones?

Asexual reproduction Signup and view all the answers

Which of the following is NOT a type of asexual reproduction?

Meiosis Signup and view all the answers

What is the two-fold cost of sex?

Time and energy to find a mate, and fewer offspring per reproductive cycle Signup and view all the answers

Why are there few organisms that only reproduce asexually in the animal kingdom?

Because sexual reproduction is more advantageous in the long run Signup and view all the answers

Study Notes

Reproductive Development

Gametogenesis is the formation of gametes (sperm and ova)
Spermatogenesis is the formation of sperm, while oogenesis is the formation of ova (or eggs)

Sperm Development

During coitus, sperm is introduced into the female reproductive tract
In the female reproductive tract, sperm undergo capacitation, which increases motility, loses membrane proteins, and changes plasma membrane fluidity

Fertilization and Development

After fertilization, the oocyte completes meiosis II and undergoes changes to prevent polyspermy
The single-celled zygote then divides by mitosis (cleavage) to increase the number of cells without increasing embryo size
The morula stage is a solid ball of cells, while the blastula stage is a fluid-filled ball of cells
Implantation marks the beginning of pregnancy
The blastocyst grows into a bilaminar embryo and undergoes gastrulation, forming the three germ layers: ectoderm, mesoderm, and endoderm
The trilaminar embryo then undergoes organogenesis, during which organs are formed

Evolution of Reproduction

Hypotheses for why asexual reproduction is not ubiquitous include:
- Beneficial mutations can be spread through the population via sex
- Harmful mutations can be purged via sex
- The Red Queen Hypothesis

Vertebrate Reproduction

Aquatic vertebrates (fish and amphibians) use external fertilization
Terrestrial vertebrates (reptiles, birds, and mammals) use internal fertilization
Amniotic eggs evolved to allow terrestrial animals to lay eggs outside of water

Reproductive Strategies

r-strategists produce many offspring with minimal parental investment
k-strategists produce few offspring with high parental investment

Male Gametes

Produced in the testes
Anatomy consists of head (acrosome), neck (mitochondria), and tail (flagellum)

Female Gametes

Produced in the ovaries
Travel through the oviduct (fallopian tube) where fertilization usually occurs
Fertilized ovum implants in the uterus to develop

Hormone Control of the Reproductive System

Hypothalamus releases gonadotropin-releasing hormone, which triggers the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
LH and FSH trigger the release of testosterone, estrogen, and progesterone
Hormones control the development of secondary sexual characteristics and the menstrual cycle in females
Decrease in estradiol and progesterone from the ovaries leads to menopause in women