ASEXUAL REPRODUCTION
Science 9 – Mr. Klasz
MITOSIS
• We have already learned about mitosis as a major way that cells
reproduce asexually.
• Cells go through the cell cycle to create, essentially, clones of
themselves.
• There are several additional methods that different kinds of cells
reproduce asexually.
ASEXUAL REPRODUCTION AT A GLANCE
• What do all asexually reproducing cells have in common?
• They are all somatic cells
• Every cell in your body is a somatic cell, with the exception
of sperm (males) and eggs (females). These cells are
gametes (more on this later)
• All asexually reproducing cells produce diploid cells.
(represented as 2n)
• This means that each cell has TWO copies of each
chromosome
• This is why interphase is so important!
ASEXUAL REPRODUCTION IN PROTISTS
• The kingdom Protista contains unicellular organisms
such as the ameoba.
• These organisms DO contain a true nucleus.
• As such they can undergo mitosis.
ASEXUAL REPRODUCTION- VIA BINARY FISSION
• In this process, a single chromosome (carrying a complete set
of DNA) is duplicated. Once this duplication has taken place,
the two identical chromosomes go to opposite ends of the cell.
The cell then splits and two new cells are formed.
• This entire process happens in 20 minutes!
• Bacteria, which belong to the kingdom Monera, produce using
binary fision.
• These unicellular organisms do not contain a true nucleus, and
therefore do not need to undergo mitotic division
ASEXUAL REPRODUCTION VIA FRAGMENTATION
• This type of asexual reproduction happens in members of the
Fungi kingdom
• Moulds, yeasts and mushrooms are all types of Fungi.
• Fungi grow over the surface, and into the bodies of other
organisms
• They are made up of many thin filaments called hyphae
• Fragmentation happens when a small fragment (piece) of the
hyphae breaks off and develops into a new organism.
• The fragment must contain a nucleus.
ASEXUAL REPRODUCTION VIA SPORES
• Moulds reproduce this way.
• Spores are reproductive cells that can grow into a new
organism if it is able to attach to a suitable host.
• Spores are released from “bulbs” on that grow up from
the surface of the substance.
• These bulbs are called sporangiums
• The spores break out of the sporangiums and become
air born (floating in the air). They then land and produce
a new organism if they land in a suitable location.
ASEXUAL REPRODUCTION-BUDDING
• In some species, budding occurs to produce an identical offspring
• The first step is to create a copy of the nucleus
• Then a tiny bud begins to form on the cell wall.
• The bud contains the new nucleus, and continues to grow larger (similar to
mitosis).
• It eventually breaks away.
• Yeast-unicellular fungi-use budding
• Some animals such as sponges, can reduce asexually by budding. A cell,
which is usually near the base of the organism, undergoes mitosis and cell
division to produce a new group of cells, or a bud. When it becomes fully
grown, it detaches and is independent.
OTHER ASEXUAL REPRODUCTION IN ANIMALS
• Some animals, like flatworms, can break into two
and then regenerate body parts to have two
identical organisms
• The end with the head will grow a new tail, and
the end with the tail will grow a new head.
STILL TO COME
•
Asexual Reproduction in Plants