Biology - Modes of Reproduction Flashcards
What is asexual reproduction? What process is sometimes used by organisms for this?
The process where genetically identical offspring are produced from one parent without the fusion of gametes. Mitosis is sometimes used.
What are gametes?
A reproductive cell of an organism
What is mitosis? What are chromosomes?
- For both animal and plant cells
- A type of cell division, and the chromosome numbers in genetically identical daughter cells are the same as the parent.
- Chromosomes consist of chromatid and a centromere. When preparing for division, the single chromatid breaks into two, forming sister chromatids. They are still one chromosome as there is only one centromere, until they are divided into two chromosomes.
What are the four stages of mitosis?
Prophase, metaphase, anaphase and telophase. Interphase occurs before mitosis to prepare for cell division, where cell growth and DNA replication occurs.
What happens during each stage of mitosis?
Prophase: DNA condenses into chromosomes to become more visible. The membrane around the nucleus disappears.
Metaphase: Chromosomes line up randomly in the equator of the cell.
Anaphase: Sister chromatids are pulled to different ends of the cell, where each will become a new chromosome.
Telophase: Nuclear membranes form around the chromosomes at each end of the cell.
Why is mitosis important?
Animal and plant cells undergo mitosis. It allows asexual reproduction to occur, produces new cells for growth in multicellular organisms, and repairs damaged tissues by replacing dead/damaged cells with new ones.
What are the advantages and disadvantages of asexual reproduction?
Adv:
- Only one parent required
- No fusion of gametes
- All beneficial qualities passed down to offspring
- Faster than sexual reproduction
Disadv:
- No genetic variation; not well-adapted to environmental changes. e.g. should the parent be vulnerable to a disease, their offspring will be vulnerable as well
What is sexual reproduction? What is the chromosome number of gametes and how are they produced?
It is the process involving the fusion of two gametes to form a zygote, producing genetically non-identical offspring. Gametes contain half the number of chromosomes (23) as normal body cells (46), and are produced by meiosis.
What is meiosis?
Most diploid organisms undergo meiosis during gamete formation. The halving of the chromosome number allows fusion of haploid gametes to form the zygote. The offspring developed from the zygote has the same chromosome number as the parents of the zygote, which ensures genetic stability in generations. Meiosis is the reduction division which produces four genetically dissimilar daughter cells. This is an essential process prior to fertilisation in sexual reproduction.
What is a haploid and diploid cell?
Diploid: Cell with two sets of chromosomes (46), one from each parent.
Haploid: One set of chromosomes
What are the characteristics of a diploid cell?
- 23 PAIRS of chromosomes (two sets of 23 = 46)
- Each pair has the same shape, size and sequence of genes
- Homologous chromosomes: each pair is from each parent
What is the process of meiosis?
PMAT I and II, meiosis I is the separation of homologous chromosomes, II is the separation of sister chromatids.
Why is meiosis important?
- Produces haploid gametes
- Promotes genetic variation (gametes are genetically dissimilar), which is essential for evolution and allows the species to better adapt to environmental changes.
What are the advantages and disadvantages of sexual reproduction?
Adv:
- Offspring may inherit beneficial qualities from both parents
- Genetic variation
Disadv:
- Two parents required
- Fusion of gametes required
- Slower method of producing offspring
What are the differences between asexual and sexual reproduction?
Asexual:
- No fusion of gametes
- One parent required
- Genetically identical offspring
- Quicker
Sexual:
- Two parents required
- Fusion of gametes required to form the zygote
- Slower process
