2. Essential Knowledge
2.c.2 Organisms respond to changes in their
external environments.
Examples: Taxis and Kinesis in animals,
chemotaxis in bacteria, & sexual reproduction
in fungi.
3. Taxis and Kinesis in animals
Taxis is a non-directional movement of organisms due to stimuli such as
gas exposure, light intensity and temperature. This can be positive or
negative for the organism.
Kinesis is a change in activity level in animals that are dependent on a
stimuli. This is neither positive nor negative because the stimuli does not
attract or repel the organism.
4. Examples of Taxis and Kinesis in animals
This connects to the essential knowledge because it proves that animals
move and respond to changes in their environments.
Example: Positive taxis in Fruit flies; the stimuli includes food, light and
gravity. Adult fruit flies are attracted to bright lights so they tend to move
towards the lighting as opposed to darkness.
Example: Kinesis in cockroaches would be light. Cockroaches are neither
attracted or repelled to light, they simply scatter and elude energy. This is an
example of stimuli that causes movement to be random.
5. Chemotaxis in bacteria
Chemotaxis is the response of organisms because of chemical stimuli
Somatic cells, bacteria and other single-celled and multi-celled organisms
direct their movement according to the chemicals in their environment. This
is important for bacteria to find food by swimming to the highest
concentration or to swim away from poison.
This connects to the Essential knowledge because it explains how organisms
move around and make changes based on their environment. If a bacteria
was to need food and there was none in their environment, they would
swim to a higher concentration to find food. In the same way, bacteria can
swim from chemicals like poison that may be in or entering their
environment.
6. Sexual reproduction in fungi
Sexual reproduction allows fungus to adapt to new environments. Sexual
reproduction in fungi consists of three stages: Plasmogamy, Karyogamy, and
meiosis.
Sexual reproduction allows fungus to adapt to new environments, proving
the essential knowledge statement because sexual reproduction would be
the change in environment, that would then allow the fungus to move and
adapt to different environments.
