Types of Reproduction Chapter Notes | Science for Grade 6 PDF Download

Introduction

Reproduction is how living things, like animals and plants, make new living things. This chapter explains two main types of reproduction: asexual and sexual. Asexual reproduction involves one parent and creates offspring that are exactly like the parent. Sexual reproduction involves two parents and creates offspring that are different from both parents. We will learn how sea stars, plants, and other organisms reproduce, and the advantages and disadvantages of each type. This helps us understand how life continues and grows in nature.

How can one organism make more organisms?

• Regeneration is when a new organism grows from a piece of the parent. For example, Sea stars increased in number even after being cut up. This happens through a process called regeneration. 
• Some plants can also reproduce without seeds, using parts like leaves or stems. This is called vegetative reproduction, a type of asexual reproduction.
• Asexual reproduction means one parent or part of it makes a new organism. The new organism is exactly the same as the parent in its genes.

How do other organisms reproduce asexually?

• Many plants, animals, and other organisms can reproduce asexually. Not all organisms use the same way to reproduce asexually.
• Hydra, a small water animal, reproduces by budding. Budding is when a new organism grows on the parent’s body.

Why do some organisms have two parents?

• In asexual reproduction, offspring are exactly like the parent.
• In sexual reproduction, offspring are not exactly like their parents.
  • Offspring from two parents have different traits, like eye or hair color.
  • Sexual reproduction combines genetic material from two parents.
  • Each parent gives half of the genes to the offspring.
  • Offspring have two copies of each chromosome, one from each parent.

What are the advantages and disadvantages of sexual and asexual reproduction?

A Closer Look: Cloning and the Future

• Cloning is a type of asexual reproduction done in a lab.
• It creates identical copies from a cell or group of cells.
• The clone has the same genes as its parent.
• Farmers and scientists use cloning to copy organisms with good traits, like plants with big flowers.
• Scientists have cloned animals like sheep, pigs, deer, and horses.
• The first cloned mammal was a sheep named Dolly, born in 1996.
• Dolly was cloned at the Roslin Institute in Edinburgh.
• Cloning helped learn more about making copies of animals.
• In 2001, a gaur, a type of wild cattle, was the first endangered species cloned.
• Cloning does not add genetic variety to a species.
• Some worry about the high cost and ethical issues, like cloning humans.