Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.
When you examine the kingdom protista you might think you have been carried away to a strange land filled with strange creatures. Algae, amoebas, and slime molds, oh my! But despite all belonging to the same kingdom, these organisms have little in common. They look different, move by different means, and feed in different ways. They don't fit into any other group because they are not animals, plants, bacteria, or fungi. We call these leftovers of the living world the protists.
As different as protists may be, they all have to reproduce. This lesson will discuss how protists create new protists through both asexual reproduction and sexual reproduction.
Asexual reproduction requires one parent and produces offspring that are genetically identical to that parent. In addition to the convenience of self-reproduction, asexual reproduction can occur more frequently and produce rapid population growth. Because of this, asexual reproduction is the primary method protists use to reproduce.
The following are types of asexual reproduction that occur in protists:
- Binary fission: Binary fission occurs when a single protist divides its nucleus and then divides itself into two separate organisms.
- Multiple fission: Multiple fission is similar to binary fission, except the nucleus can divide and form many daughter nuclei. The organism will then divide into separate organisms for each nuclei that has been created.
- Budding: Budding occurs when a new organism grows from the body of the parent organism. The new organism may separate from the parent or remain attached, forming colonies.
Sexual reproduction in protists requires two parent organisms. Both organisms contribute genetic material to the offspring. The benefit of sexual reproduction is that it creates this genetic variability. Sexual reproduction techniques that occur in protists are conjugation and alternation of generations. Conjugation occurs when two protists of the same species come together and form a temporary union. They exchange genetic material during this union. When the two protists separate, they are genetically different from the original organisms.
Sexual reproduction also takes place as part of a protist life cycle called alternation of generations. During the first phase of their life cycle a protist will produce spores . Each spore contains half of the parent organism's genetic material. These are released into the environment where they can live and grow, creating the first generation of the organism's life cycle. In this case, generation means phase and is still referring to a single organism, not the offspring like we're used to. In the second generation, or phase, of the protist's life cycle, the organism that grew from the spore releases copies of itself into the environment that act as gametes, or reproductive units. When two gametes come together they fuse to form a zygote with a full set of genetic material that will grow into the protist. In the end, both generations of the protist act together to reproduce.
The kingdom protista contains organisms we call protists, which are neither animal, plant, fungi, nor bacteria and can include algae, amoebas and slime mold. Asexual reproduction is the most common among protists. Protists can reproduce asexually through binary fission, one nucleus divides; multiple fission, many nuclei divide; and budding. During both types of fission the organism replicates its nucleus and divides to form new organisms. Budding occurs when a new organism grows from the body of its parent.
They can, however, also reproduce by sexual reproduction. Protists reproduce sexually through the processes of conjugation and alternation of generations. Conjugation is a temporary union of protists in which they exchange genetic material. Alternation of generations is a life cycle in which a protist releases spores with half of its chromosomes into the environment, and they form a first generation organism. The first generation then releases sexual reproductive units called gametes into the environment. When two gametes come together they form a zygote that contains a full set of genetic material and will develop into the second generation and the cycle will start again.
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