Flashcards in [Chapter 39] Reproduction Deck (172)
What is a zygote?
The first cell of a new individual formed by the fusion of one gamete from each parent.
Give a short description of the genetic basis of sexual reproduction.
Meiosis and the formation of gametes typically occur in two prospective parents. At fertilization, a gamete from one parent fuses with a gamete from the other and forms the first cell of the new individual—the zygote.
Give a short description of asexual reproduction.
A single organism produces its own offspring. In asexual reproduction, one parents has all its genes represented in its offspring.
Is sexual or asexual reproduction better for an environment that does not vary over time?
Asexual reproduction is better, as the gene combinations that allowed the parent to reproduce can be expected to do the same for their offspring.
Why is sexual reproduction good for environments that change over time?
Every individual inherits a different combination of parental genes, increasing the odds that some offspring will have a gene combination that suits the changing environment.
Why is sexual reproduction costly?
Only half of a parent's genes end up in the offspring; resources and energy must be allocated to forming gametes. Timing of gamete formation must be synchronized between partners, and there has to be a partner.
Why does sexual reproduction require timing?
Sperm in one individual must mature at the same time as eggs of another individual.
What is internal fertilization?
The union of sperm and egg within the female body.
What is yolk?
A thick fluid that contains proteins and lipids that nourishes the embryo until it can feed.
How are humans nourished in embryo?
Through a nearly yolk-less, fertilized egg and through physical changes in the mother's bloodstream.
True or False: Separation into male and female sexes requires special reproductive cells and structures, and neural and hormonal control mechanisms.
True. They also require "forms of behaviour", whatever the heck that means.
What are the six stages of animal reproduction and development?
1. Gamete Formation2. Fertilization3. Cleavage4. Gastrulation5. Organ Formation6. Growth, Tissue Specialization
Describe the stage Gamete Formation.
Eggs form and mature in female reproductive organs. Sperm form and mature in male reproductive organs.
Describe the stage Fertilization.
A sperm penetrates an egg. Their nuclei fuse, and a zygote is formed.
Describe the stage Cleavage.
Mitotic cell divisions form a ball of cells called a blastula. Each cell gets regionally different parts of the egg cytoplasm.
A ball of cells that enclose a cavity (blastocoel) filled with their own secretions.
Describe the stage Gastrulation.
Cells self-organize as an early embryo (a gastrula) that has two or three primary tissue layers, which make the germ layers of a new individual.
An early embryo.
What are Germ Layers?
The forerunners of the adult animals's tissues and organs.
What are the Germ Layers of the Gastrula?
The Ectoderm, Endoderm, and Mesoderm.
What is the Ectoderm?
The outer germ layer. It forms first, and gives rise to nervous tissue and to the outer layer of skin or other body covering.
What is the Endoderm?
The inner germ layer, it is the tart of the respiratory tract and gut linings.
What is the Mesoderm?
In most kinds of animals, the mesoderm forms between the ectoderm and the endoderm. This layer is the source of all muscles, connective tissues, and the circulatory system.
Describe the stage Organ Formation.
Details of the body plan fill in as different cell types interact and form tissues and organs in predictable patterns.
Describe the stage Growth, Tissue Specialization.
The final stage of animal development, the tissues and organs grow in size and slowly begin to take on their final sizes, shapes, proportions, and functions.
What does sperm consist of?
Parental DNA and a bit of equipment that helps in swim to and penetrate an egg.
What is an oocyte?
An immature egg that has far more cytoplasm compared to the sperm. The cytoplasm has yolk proteins that will nourish a new embryo, mRNA transcripts for proteins that will by translated in early development, tRNAs and ribosomes to translate the mRNA transcripts, and proteins required to build mitotic spindles.
What is cytoplasmic localization?
When certain components are not distributed all through the egg cytoplasm, they are localized in one particular region or another. It helps guide development.
What is cytoplasmic localization a feature in all of?
Oocytes (immature egg).