Development Of Organisms Flashcards
(39 cards)
What are chromosomes?
Long thread-like structures located inside the nucleus that contain DNA
Chromosomes carry genetic information in the form of genes.
What is mitosis?
A type of nuclear division that produces genetically identical cells
Mitosis maintains the chromosome number and ensures genetic consistency.
What is the chromosome number in humans?
46 chromosomes in each body cell except in gametes
Humans have 23 pairs of chromosomes.
Define diploid cells.
Cells that have two sets of chromosomes (2n)
In humans, diploid cells contain 46 chromosomes.
Define haploid cells.
Cells that have only one set of chromosomes (n)
Gametes are haploid with 23 chromosomes.
What is the importance of mitosis?
- Ensures daughter cells maintain the same chromosome number
- Replaces damaged cells
- Forms the basis of asexual reproduction
- Supports organism growth
Mitosis is crucial for maintaining genetic continuity.
What is meiosis?
A special type of cell division that reduces the chromosome number by half
Meiosis produces four haploid gametes.
What is the significance of meiosis?
Produces haploid gametes ensuring the diploid number is restored at fertilization
It allows for genetic variation in offspring.
What is a stem cell?
A cell that can divide an unlimited number of times and can become specialized
Stem cells provide new cells for growth and replacement of damaged cells.
How do cancers form?
Through uncontrolled cell division due to mutations in genes that control cell division
Environmental factors can cause mutations leading to cancer.
Define asexual reproduction.
The production of genetically identical offspring from a single parent without the fusion of gametes
Offspring produced by mitosis are called clones.
What are the types of asexual reproduction?
- Binary fission
- Budding
- Vegetative propagation
These methods allow for rapid population increase.
What are the advantages of vegetative propagation?
- Only one parent required
- Rapid reproduction
- Surer reproduction
- Genetically identical offspring
Beneficial traits are passed directly to offspring.
What are the disadvantages of vegetative propagation?
- Lack of genetic variation
- Disease transmission from parent
- Over-crowding issues
Genetic uniformity can be detrimental in changing environments.
What is sexual reproduction?
The fusion of two nuclei to form a diploid zygote producing genetically different offspring
It increases variation within the species.
List the parts of a typical flower.
- Pedicel
- Receptacle
- Sepals
- Petals
- Stamen
- Carpel
Each part plays a crucial role in plant reproduction.
What is pollination?
The transfer of pollen from the anther to the stigma
This can occur via wind or insects.
What is self-pollination?
Transfer of pollen to the stigma of the same flower or another flower on the same plant
Results in offspring that are often weaker and less adaptable.
What is cross-pollination?
Transfer of pollen to the stigma of different plants
Results in greater genetic variation among offspring.
What are the advantages of cross-pollination?
- Inherits strong genes
- More viable seeds produced
- Greater variety of offspring
Increases survival chances during environmental changes.
What is fertilisation?
The fusion of male and female gametes
In flowering plants, pollen grains are the male gametes.
What is germination?
The process during which a seed develops into a new plant
Requires water, suitable temperature, and oxygen.
What are the conditions necessary for seed germination?
- Water
- Suitable temperature
- Oxygen supply
Each condition plays a critical role in the germination process.
What is the structure of a broad bean seed?
- Seed coat (testa)
- Micropyle
- Hilum
- Embryo (plumule and radicle)
- Cotyledons
Each part serves a specific function in seed development.
