reproduction system

How is the reproductive system different from most other body systems?

It is not aimed toward homeostasis and is not necessary for individual survival; it is required for species continuation.

What is the fundamental difference between sexual and asexual reproduction?

Sexual reproduction involves genetic contribution from two individuals, while asexual reproduction involves one individual.

What is parthenogenesis in animals?

An asexual reproductive strategy where an unfertilized egg develops into an embryo. It is not cloning, as genetic recombination can occur.

What are gametes in sexual reproduction?

Haploid cells (sperm and egg) that fuse to form a diploid zygote, combining genetic material from two parents.

What is the "reproductive handicap" of sexual reproduction?

An asexual population can outgrow a sexual one if each individual produces two surviving offspring, because asexual reproduction is faster and more efficient numerically.

What is a potential evolutionary advantage of sexual reproduction?

It allows beneficial mutations from different individuals to combine and enhances adaptation to changing environments.

What is the Red Queen Hypothesis in relation to reproduction?

It proposes that sexual reproduction, by generating genetic diversity, helps species continuously adapt to changing environments, akin to "running to stay in place."

What characterizes an r-selected reproductive strategy?

Producing many offspring with minimal parental care or nourishment, where only a tiny fraction survive (e.g., many fish spawning).

What characterizes a K-selected reproductive strategy?

Producing relatively few offspring with substantial parental investment in nourishment and protection, leading to high survival rates (e.g., humans, elephants).

What is the difference between oviparity, ovoviviparity, and viviparity?

Oviparity: young develop in eggs outside the mother. Ovoviviparity: eggs develop inside the mother but without direct nutrient transfer. Viviparity: young develop inside the mother with direct nutrient transfer via a placenta.

Are all three reproductive modalities (oviparity, ovoviviparity, viviparity) found in reptiles?

Yes, all three are observed in reptiles, including snakes and lizards.

What are the primary reproductive organs in animals and what do they produce?

Gonads: testes (produce sperm) and ovaries (produce eggs). They also secrete sex hormones.

What is a key difference between spermatogenesis and oogenesis?

Spermatogenesis produces four functional sperm continuously; oogenesis produces one functional egg and polar bodies, and is prolonged, often completed long after formation begins.

What is the X-Y system of genetic sex determination?

Males are heterogametic (XY) and females are homogametic (XX). Found in mammals and some other vertebrates.

What is the Z-W system of genetic sex determination?

Females are heterogametic (ZW) and males are homogametic (ZZ). Found in birds, snakes, and some lizards and turtles.

In mammals, what gene on the Y chromosome initiates male development?

The SRY gene (sex-determining region Y), which produces testis-determining factor (TDF).

What is Temperature-Dependent Sex Determination (TSD)?

A system where the sex of offspring is determined by incubation temperature during a thermosensitive period, common in many reptiles and fish.

What is a major disadvantage of Temperature-Dependent Sex Determination?

A narrow temperature range for persistence; thermal pollution (e.g., climate change) can skew sex ratios or eliminate populations.

How does the herbicide atrazine act as an endocrine disruptor?

It induces aromatase expression, converting androgens to estrogens, leading to hermaphroditism and demasculinization in amphibians like frogs.

What is obligate parthenogenesis?

An asexual mode where a species consists only of females that reproduce via unfertilized diploid eggs, with no males (e.g., some whiptail lizards, Brahmini blind snake).

What is facultative parthenogenesis?

The ability to switch between sexual and asexual reproduction. It can occur in some reptiles, birds, and snakes, often as a last-resort strategy, but often results in reduced offspring viability