Reproduction and Interrelation in Living Organisms
Reproduction in Living Organisms
Unicellular and Multicellular Reproduction
- In unicellular organisms, reproduction usually involves the division of a single cell.
- In multicellular organisms, reproduction is carried out at both the cellular and organismal levels.
Asexual Reproduction
- Fragmentation: This consists of the division into fragments that give rise to new individuals. When fragmentation is not spontaneous and occurs because of an injury, it is called regeneration.
- Budding: This originates in a group of cells that form a bud, generating another individual. The new individual may stay attached or separate. If they remain attached, they often form colonies, as seen in sponges or polyps.
Sexual Reproduction
In most cases, there is a reproductive system consisting of gonads. There are two types:
- Testicles, which generate sperm.
- Ovaries, which produce eggs.
The process is called fertilization, which creates a zygote. Some animals are hermaphrodites.
Alternating Reproduction
This is often seen in simpler animals. They reproduce asexually, forming buds that separate into jellyfish.
Reproduction in Plants
Asexual Reproduction
Usually produced by vegetative propagation, which leads to new plants without the intervention of sex cells.
- Bulbs: In leeks and garlic, a bud forms in the bulb, called a bulbil, which can give rise to new plants.
- Tubers: In potatoes, stems have buds called “eyes” that can give rise to new plants.
- Runners: In strawberries, a long stem on the ground, called a stolon, reaches another plant. When it is mature, the runner disappears, leaving independent plants.
- Rhizomes: These are root-like structures in some plants that generate fragments, leading to new plants.
Asexual Reproduction by Humans
- By stake: A fragment of the stem is buried, and roots are expected to form.
- By layering: A branch of the mother plant is buried. When the branch is mature, it is cut and separated, forming a new plant.
- By graft: A piece of stem is inserted into another of the same species but a different variety. The new plant will have improved characteristics and is usually used for fruit trees.
Sexual Reproduction
In a flower, the male reproductive system consists of stamens, and the female reproductive system consists of the ovaries.
Alternating Reproduction
This occurs in flowers, mosses, and ferns. Gametes are called gametophytes or sporophytes.
Interrelation in Living Things
The function of interrelation occurs at the cellular level and the organizational level.
- In unicellular organisms, the cellular level is the same as the organismal level, as the organism consists of a single cell. They move or form spores.
- In multicellular organisms, interrelation occurs at both the cellular and organismal levels.
Coordination
Animals detect external changes as well as those that originate within their own bodies.
- External changes take place in the environment.
- Internal changes take place within the organism’s body.
Response to Perception
Responses can be mechanical, chemical, thermal, or to light.
In vertebrates, responses are produced in the brain, which is formed by:
- Medulla: Controls heartbeat and breathing rhythm.
- Cerebellum: Coordinates movements.
- Brain: Responds to voluntary movements. Spinal cord reflexes are also developed here.
Plants also detect environmental stimuli, responding with tropisms and nastias.
- Tropisms are permanent movements, such as geotropism, phototropism, and hydrotropism.