Meiosis & Sexual Reproduction Flashcards
How does sexual reproduction occur?
When a sperm cell (produced in the testes) is joined by an egg cell (produced in the ovaries), forming a genetically unique zygote.
What are the stages of sexual reproduction?
1st: Mating
2nd: Fertilization
3rd: Development
What is mating?
The process of gametes arriving in the same place at the same time
What is fertilization and what are the two ways of it happening?
Fertilization: Union of a sperm cell and egg cell
1) External Fertilization - A sperm cell and an egg cell of the same species unite outside of the parents’ bodies
-common to aquatic animals like fish, frogs, birds, and plants like moss and ferns
2) Internal Fertilization - Sperm cells are deposited inside the female’s body where they meet an egg cell
-used by land dwelling animals and even some aquatic animals like sharks and orcas
-Sperm cell penetrates egg cell, forming a zygote, undergoing mitosis and cell division to become an embryo
-Embryo develops & nourished inside the mother’s body, and offspring is often protected by their parents
What is the third way of fertilization?
Plants that grow from seeds need pollination for fertilization
-Pollen can be transferred by the wind/animals (bees, birds)
What is pollination and how does this occur?
Pollination: A type of internal fertilization used by most plants; male gametes (pollen) are transferred from the male reproductive part of a plant to the female reproductive part of a plant
The process:
i) Pollen grains carry sperm cells in a protective case to the ovules, which contain the egg cells
ii) When pollen lands on the female part of the plant, a pollen tube forms and delivers the sperm cells to the egg cells
iii) The fertilized egg becomes a zygote, which grows into an embryo through mitosis and cell division
iv) The embryo is protected by a seed coat
What is the third stage of sexual reproduction?
Development:
Human Prenatal Development - Early development of an organism before birth
-Development of the human zygote occurs in stages:
1) Embryonic stage - 0-8 weeks
2) Fetal stage - 8-38 weeks
-The zygote (fertilized egg) undergoes mitosis and cell division
-Mass of dividing cells travels and implants to the lining of the uterus
What is meiosis?
The process in which haploid cells are produced from a diploid parent cell
-required for sexual reproduction
-results in genetic diversity; inherited genetic differences in a species
What’s the diploid number?
The # of chromosomes in the body cell of an organism that has two sets of chromosomes
What’s the haploid number?
The # of chromosomes in a gamete cell that has one set of chromosomes (1/2 the chromosome number of the parent)
-Haploid: one set of chromosomes
Ex. Human gamete cells have 23 chromosomes
What are gametes?
Specialized cells that are necessary for reproduction that have a haploid number (Ex. 23 chromosomes)
-Male Gamete - Sperm
-Female Gamete - Egg
What is fertilization?
The fusion of a male and female gamete
-Results in a diploid cell called a zygote
-Sperm (n) + Egg (n) = Zygote (2n)
What’s an embryo?
A single cell diploid zygote undergoes mitosis and cell division many times to result in a multicellular embryo
What’s the process of Meisosis I?
-Chromosomes were duplicated during Interphase and are now sister chromatids joined by a centromere
PMAT:
Prophase I:
-Nuclear membrane begins to disappear
-DNA condenses into duplicated chromosomes
-Homologous chromosomes are paired
Metaphase I:
-Pairs of homologous chromosomes line up at the middle of the cell
Anaphase I:
-Homologous chromosome pairs separate and move to opposite ends
Telophase I:
-Results in two diploid daughter cells
What happens in Meiosis II?
-Dna isn’t replicated before Meiosis II
-Sister chromatids line up across the middle of the cell and are pulled to opposite ends of the cell
-Results in four haploid gametes
-Gametes have half the number of chromosomes as the parent cell
