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ZingPath: Reproductive Systems

Breeding Zebra Danio Fish: An Introduction to Sexual Reproduction

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Lesson Focus

Breeding Zebra Danio Fish: An Introduction to Sexual Reproduction

Life Science

Learning Made Easy

Learners are introduced to sexual reproduction and fertilization by studying the zebra danio fish, and creating the appropriate spawning conditions.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Explain that sexual reproduction requires a male organism producing sperm and female organism producing an egg.
  • Explain that fertilization is the joining of the female egg cell and the male sperm cell.
  • Accurately predict the number of chromosomes the sperm and egg each carry based on the number of chromosomes the fertilized egg contains.

Everything You'll Have Covered

Reproduction is a biological process by which organisms create new individual organisms. Every existing plant, animal and other living organism is the result of biological reproduction, and all continuing species reproduce in some way. The two main classifications of reproduction are sexual and asexual reproduction.

Sexual reproduction, which includes human reproduction and most other animals, requires the participation of two individuals of the opposite sex. During sexual reproduction, an embryo is formed when an egg produced by the female is fertilized by sperm from the male (as during human reproduction).

In sexual reproduction, the male and female each donate half their chromosomes, which carry genes, to the young, resulting in offspring with a mix of inherited genes. Chromosomes are microscopic thread-like structures that are made up mainly of DNA. Different species have different amounts of chromosomes that are donated to their offspring. For example, a human has two sets of 23 chromosomes for a total of 46 chromosomes. A copy of each chromosome comes from that person's father and the other from their mother. Whereas, a tiger carries 19 chromosomes from each parent for total of 38 chromosomes, and a horse carries 32 chromosomes from each parent with a total of 64 chromosomes.

The big advantage of sexual reproduction is that it results in variations among the offspring. This variability helps ensure that some individuals will have genes to survive changing environments.

As stated earlier, genes are donated from each parent via fertilization. There are two methods by which fertilization can take place with animals; external and internal. External fertilization is the process by which the eggs are fertilized outside of the female body. This process is very common in aquatic animals such as certain species of fish, coral, clams, and frogs. Alternatively, internal fertilization describes animals where the egg is fertilized within the female reproductive system. This process is widely used among most non-aquatic animal species.

Asexual reproduction is the process of an individual reproducing without the help of any other member of that species. Therefore, only one parent is needed, which results in its offspring being genetically identical to the parent, (i.e., a clone) and other offspring. Organisms that reproduce using asexual reproduction generally produce significantly more offspring because they do not have to rely on another organism within the species for participation, it is an efficient way to reproduce under harsh environmental conditions, and there is no parental care of the young. The lack of variability in the population could mean that the organism could be wiped out in a changing environment. For example, bananas have lost the ability to reproduce sexually, so a virus that mutates and attacks bananas with more power could result in the eradication of the species.

Although a majority of animals reproduce through sexual reproduction, there are some species that can switch between sexual and asexual reproduction as circumstances demand. Most of these rare organisms are plants, such as strawberries.

Overall, asexual reproduction is much easier and faster than sexual reproduction, it does not create variation within the species. Sexual reproduction creates diverse organisms that can adapt to their environments and live longer.

Tutorial Details

Approximate Time 2 Minutes
Pre-requisite Concepts Chromosomes, sperm, egg
Course Life Science
Type of Tutorial Concept Development
Key Vocabulary ammonification, assimilation, consumer