Plant and Animal Responses Flashcards
What is the function of the cerebrum?
- receives sensory information, interprets it, and sends out motor impulses to bring about a voluntary response
- site of learning, reasoning, intelligence, personality, memory and conscious thought
What is the function of the cerebellum?
coordinates muscle movement such as balance and fine movement
What is the function of the medulla oblongata?
- controls non-skeletal muscle
- control centre for the autonomic nervous system
- contains regulatory centres - cardiac and respiratory centres
What is the function of the hypothalamus?
- controls most of the body’s homeostatic mechanisms
- links the nervous and endocrine systems
What is the function of the pituitary gland?
regulated by the hypothalamus, stores hormones such as ADH
What are three commercial uses of plant hormones?
- control fruit ripening
- rooting powders
- hormonal weed killers
What hormone is used to control fruit ripening and how?
Ethene is used to speed up ripening of fruit such as bananas, apples and tomatoes.
Restricting ethene can also be useful to delay ripening of fruit. Low oxygen levels, high carbon dioxide levels, and a low temperature prevent ethene synthesis.
What hormone is used in rooting powders and why?
Synthetic auxins are used in rooting powders because they stimulate the growth of roots from cut stems.
They are used to encourage cuttings to make roots.
What hormone is used in hormonal weed killers and why?
Synthetic auxins are used as selective weed killers to kill broad-leaved weeds (dicotyledonous) in fields of narrow-leaved monocotyledons (e.g., wheat).
The auxins increase the rate of growth of the weeds. The weeds are unable to absorb enough nutrients and energy from their surroundings to keep up with the accelerated growth rate and soon die.
What hormones coordinate leaf fall in deciduous plants and how?
Levels of cytokinins in a leaf decline, and the leaf will start to age and brown.
The level of auxins in the leaf also starts to decrease, which has two effects:
1, Cells in the abscission layer (between the petiole and the stem) become more sensitive to ethene.
2, More ethene is produced.
This increases production of cellulase, which digests cells in the abscission layer, causing the leaf to fall.
What hormone coordinates seed germination and how?
Water is absorbed by the seed. Gibberellins diffuse from the embryo to the aleurone layer, where they stimulate the production of amylase. Amylase hydrolyses the starch food store, thus releasing glucose for the embryo. Germination begins.
What hormone coordinates stomatal closure and how?
When flowering plants experience water stress, they close their stomata. This is brought about by abscisic acid which binds to receptors on guard cells. This causes a change in pH in the cytoplasm, and both positive and negative ions leave the guard cell. The water potential of the cell increases, causing water to leave the cell, and lose turgidity. The stomata closes.
What are some chemical produced by plants to defend themselves from herbivory?
- tannins
- alkaloids
- pheromones
How are tannins a defence against herbivory?
they reduce nutritional value of plants by preventing digestion of proteins in herbivores and can be toxic
How are alkaloids a defence against herbivory?
they give plants a bitter taste and can be toxic
How are pheromones a defence against herbivory?
plants being grazed release pheromones which alert some nearby plants to increase tannin production
