Chapter 7 Reproduction

Reproduction

The biological process by which living organisms produce new individuals, maintaining the continuity of their species.

Asexual Reproduction

A mode of reproduction involving a single parent, resulting in offspring that are genetically identical to the parent
Occurs through fragmentation, budding, and gemmulation
Pro: fast, less resources, effective for settling in new areas
cons: lack of genetic variability

Sexual Reproduction

A mode of reproduction involving two parents, leading to genetically unique offspring due to the combination of genetic material.
Only in eukaryotes, occurs with hermaphroditic and bisexual species, and through meiosis and fertilization.
Pros: increased variability, good mutations spread quickly
cons: twofold cost (resources and time), more energy needed, more complicated

Parthenogenesis

A form of asexual reproduction where an egg develops into an individual without fertilization, common in some invertebrates and rare in vertebrates.
Types include ameiotic and meiotic
Pros: rapid population growth, good for when there is a lack of males
Cons: lack of genetic variation

Dioecious

A reproductive strategy where individual organisms are either male or female, having separate sexes.

Monoecious

A reproductive strategy where individual organisms possess both male and female reproductive organs.

Sequential Hermaphrodite

An organism that can change its sex during its life cycle, often influenced by environmental factors. ‘genetically programmed sex change’, think Nemo

Protandry

A type of sequential hermaphroditism where an organism starts as a male and can later become female.

Protogyny

A type of sequential hermaphroditism where an organism starts as a female and can later become male.

Gametogenesis

The process of forming gametes (sperm and eggs) through meiosis in the gonads.

Spermatogenesis

The process of producing male gametes (sperm) in the testes, beginning at puberty.

Oogenesis

The process of producing female gametes (eggs) in the ovaries. Originally begins at fetal development, but stopes early in meiosis 1, restarting at puberty. Characterized by unequal divisions.

Oviparity

A reproductive pattern where eggs are laid outside the body after fertilization, common in many invertebrates and some vertebrates. “Egg birth”

Ovoviviparity

A reproductive pattern where fertilized eggs develop inside the female's oviduct and using the yolk inside the egg, until being born alive. “Egg-live birth”

Viviparity

A reproductive pattern where the young develop inside the female and receive nourishment directly (ex. the placenta) and then give birth. “Live birth”

r-strategists

Organisms that reproduce quickly, producing many offspring with little parental care, and in any environment. Opportunistic species, so mostly affected by density independent factors.

K-strategists

Organisms that invest more time and resources in raising fewer offspring, typically in stable environments. Equilibrium species are mostly affected by density-dependent factors.

Fragmentation

A form of asexual reproduction where an organism breaks into pieces, each capable of growing into a new individual.

Budding

A form of asexual reproduction where a new organism develops from an outgrowth or bud on the parent organism.

Gemmulation

A form of asexual reproduction involving the formation of a new organism from a cluster of cells (gemmules) that can survive harsh conditions. ‘hibernating egg’

Internal Fertilization

A reproductive process where fertilization occurs inside the female's body.

External Fertilization

A reproductive process where gametes are released into the environment for fertilization, common in aquatic animals.

Ameiotic Parthenogenesis

The egg is formed by mitosis, making it the ‘asexual’ form of parthenogenesis. The offspring are clones.

Meiotic Parthenogenesis

A haploid egg is formed by meiosis, and the diploid condition is restored by autogamy (oocyte fuse with the polar body) or chromosomal duplication.
Haplodiploidy is a variation, sex determination system where males develop from unfertilized eggs and females from fertilized eggs

Continuous spectrum

R and K species combined. Give birth to many offspring with no care, but live very long lives in stable environments. (turtles)

Simultaneous/synchronous Hermaphrodite

Animals with both male and female organs in the same individual, with self fertilization occurring sometimes.

why are all parthenogenesis komodo babies male?

female is heterogametic (wz), male is homo (ZZ). WW is not viable, ZZ is. Each haploid ovum carries either W or Z. In the case of parthenogenesis: Restore diploid chromosome when haploid ovum fuses with a polar body (autogamy)