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5.4 Asexual Reproduction Chapter 5 Cell Growth and Division Mr. Shilala DAHS KEY CONCEPT Many organisms reproduce by cell division. Purpose of Reproduction • To make sure a species can continue. – Definition: Reproduction is the process by which an organism produces others of its same kind. 2 ways • Asexual or sexual • Asexual reproduction is the creation of offspring from a single parent. There are several types Binary Fission and Mitosis 1. Binary fission is similar in function to mitosis – Binary Fission occurs in most Prokaryotes – Binary fission produces two daughter cells genetically identical to the parent cell. parent cell DNA duplicates cell begins to divide daughter cells Binary Fission and Mitosis • Prokaryotes have no nucleus but do have DNA – DNA in the shape of single circular chromosome – Chromosome copied and attached to cell wall – When cell is twice as large membrane pinches inward – cytokinesis – Cell wall forms Advantages and Disadvantages of Asexual Reproduction • Environment determines what form of reproduction is most advantageous. – Advantages of Asexual reproduction • Favorable in environments that don’t change much. • Can be more efficient – Disadvantages • In environments that do change, identical offspring respond the same to changes in environment • Extinction can occur if genetic variation is needed – Sexual reproduction • Increases genetic diversity • 1 or more individual may survive change • Asexual reproduction itself is not more efficient, rather the associated costs of sexual reproduction are greater – Example • Two organisms each have 10 offspring • 1 reproduces asexually – All 10 can have offspring of their own • The other 1 reproduces sexually – 5 males and 5 females are produced – Only females can bear offspring – Must attract a mate » Involves energy, signals, and behaviors Some eukaryotes reproduce through mitosis. • Budding – Forms a new organism from a small projection growing on the surface of the parent. – Very common in plants Hydra bud Yeast • Fragmentation – Splitting of the parent into pieces that each grow into a new organism. – Sea Stars and Flatworms • Vegetative reproduction – Forms a new plant from the modification of a stem or underground structure on the parent plant – Sometimes referred to as cloning – Strawberries and potatoes • Regeneration – The ability to restore lost or damaged tissues, organs or limbs. – It is a common feature in invertebrates, like worms and starfish.