A harmful substance. A.Pollution B.Overharvesting C.Runoff water D.Exotic species
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Answer:
The organism selected based on sexual reproduction is tortoise and based on asexual reproduction is hydra. Both of them are explained in detail below with diagrams.
Explanation:
Tortoise: These are land dwelling reptiles and have a hard shell on their back to protect from predators. They can pull their necks inside for protection. They are different from turtles which as aquatic in nature. They mostly sleep at night and are active during day. These organisms prefer to stay isolated and are not comfortable in crowds.Tortoises have very long life span that between 80-150 years with the oldest one being 255 years.
Sexual reproduction- In most cases, females tend to be larger in size than males. They reproduce sexually by laying eggs at night. Their gametes are haploid in nature which when fused result in a diploid organism. The number of chromosome in a tortoise is 52.
The tortoise eggs can remain fertile till four years after fertilization. One single mating allows 30 eggs to be fertilized. Once the female finds the right environmental conditions, the eggs are laid.
Advantage of sexual mode of reproduction:
- Offspring produced have <em>genetic variation</em>.
- This genetic variation allows them to adapt well to the surrounding.
- All the offspring don not die of a single disease because they are genetically varied.
Disadvantages: Fewer organisms are produced.
Gap between mating season.
Hydra is a fresh water organism belonging to class Cnidaria. It's body has a radial symmetry. The body contains stinging cells known as cnidocytes, which contain <em>neurotoxins</em>. These are released when faced by a predator. Its body is made up of two layers-epidermis and gastrodermis.
If a hydra is cut in half, both the cut parts regenerate into two new hydra. Their mode of reproduction is asexual through the process of budding. a
A new bud arises in some part of the body of hydra which matures and breaks off to form a new hydra. Most hydra are fixed or senile but some of them are free moving.
Advantages of asexual reproduction:
- The population <em>multiplies</em> rapidly in favorable conditions.
- Single parent is needed.
- It's <em>faster</em> than sexual reproduction.
Disadvantages of asexual reproduction:
- <em>Limited diversity</em>
- Population becomes difficult to control.
- <em>Negative mutation</em> continue through the cell lines as there is no mixing of gametes.
