Animal reproduction


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Animal reproduction

  1. 1.  Refers to the various means by which living organisms give rise to offsprings . In both plant and animal , two main types of reproduction are observed : asexual and sexual.
  2. 2.  Commonly found in the lower animals. A group of cells develops into a new individual. Only a single organism is involved. There are different processes involved in asexual reproduction. These are fission or binary fission , budding and regeneration.
  3. 3.  It is the simplest form of asexual reproduction. This is a process is observed in single-celled animals such as the amoeba or paramecium. The cell is divided in half , forming two new individuals .
  4. 4.  It is growing of new individual from a bud. Sponges, hydra and the other lower animals reproduce by budding. In this process , the new individual animal an outgrowth of cells of the parent organism. The bud enlarges, takes the form of the parent and then breaks off as a new individual.
  5. 5.  In this process, an animal divides into one or more fragments. Each fragment regenerates and becomes a complete new individual. Examples are flatworm and marine worms. In some animals, a broken part is replaced by regenerating the missing part. Say, a starfish losses one of its arms, a new arm regenerate to replace the lost arm. Another animal that has the ability to regenerate is the earthworm.
  6. 6.  This is characterized by the joining together of two different kinds of sex cells. This is are the egg cell from the female and sperm cell from the male animal. The union of the egg and sperm is called fertilization. When the egg becomes fertilized, a new individual called zygote develops. Sexual reproduction is a characteristic of a higher animals.
  7. 7.  Fertilization can be external and internal. 1.External fertilization(outside the body) › The sperm cell and egg cell unite without physical contact with the mate. The union of the egg cell and sperm cell occurs outside the body of the animal. › Example fish and frog
  8. 8.  2.Internal Fertilization ( inside the body) › This occur in female reproductive tract. The sperm cells enters the female body to meet the egg cell to produce living organisms . Examples are shark, reptile and birds. Three groups of animals vary in producing new living individuals and caring for their young. These are the monotremes , marsupials and placentals. › a . Monotremes -animals that lay eggs. Examples: anteaters and duck-billed platypus › b. Marsupials-animals which carry their young in a pouch. Examples kangaroo, koala bear and Tazmanian devil. › c. Placentals -mammals that gives nourishment to the unborn young for a longer period of time before birth. The young animal needs nutrients and other substances in order for them to develop inside a female body. Examples: whales, cows