Why do organisms need sensory and coordination abilities?
To avoid danger, find resources and time their reproduction with favourable seasons.
Why do grasshoppers have ears on each side its abdomen?
To quicken its reflex to jump.
Define the term ‘stimuli’ with an example.
Stimuli are things which cause responses in organisms. Example, the smell of food can be a stimuli for more production of saliva in you mouth.
What is the difference between the endocrine system and the nervous system?
The endocrine system uses chemical messengers called hormones to coordinate slow and extended responses such as growth and metabolic rate whereas the nervous system communicates by rapid electrical impulses for immediate sensory and coordination needs as a vision and movement.
3 differences between endocrine and nervous system.
-endocrine system is slow whereas nervous system is quick.
- endocrine system have long term responses whereas the nervous system have short term responses.
- endocrine system consist of glands and hormones whereas the nervous system consists of nerve cells, neuron and fibres.
State 3 roles of hormones in plants
- Controlling tropisms
- for growth
- for reproduction
True or false: Hormones control the fruiting- ripening, flowering and falling of leaves in seasonal plants.
True.
What would happen if there were no hormones in plants?
The roots would grow randomly, with some of it growing directly towards the sky. Some branches would be flowering and fruiting while others would be dropping leaves. And angiosperms of the same species which flower at different times of the year, would have low chances of pollination.
How can the sensitivity of a plant tissue to a given hormone be altered?
- By changing the hormone concentration in the target tissue.
-By altering the receptor sensitivity to that hormone in the target tissue.
State 3 roles of the hormone auxin.
- responsible for cell division and growth in cell size.
- prevents abscission
-Involved in apical dominance and various tropisms.
Example of an auxin is?
IAA, indole acetic acid
Example of an auxin is?
IAA, indole acetic acid
State 3 roles of the hormone cytokinin
- promotes cell division in plant roots and shoots.
-promotes growth of buds
-delays senescence and activate dormant buds.
Example of the hormone cytokinin
Zeatin
What are 3 roles of the hormone ethylene.
- responsible for senescence process
- promotes the ripening of the fruit
- affects plant functions such as abscission of leaves, seed germination and drooping of leaves.
State the 2 roles of abscisic acid (ABA0)
- maintains dormancy in seeds and buds
- stimulates the closing of stomata.
state 3 roles of the hormone gibberellins
- responsible for cell division and growth in cell size
- causes elongation of stems
- stimulate pollen tube growth
What is the function of receptors?
To sense stimuli.
What is the function for the communication system?
To carry the message between the receptors and effectors.
What is the function of effectors?
Are muscles and glands that act out the response.
Describe asymmetrical animals and give an example.
Are animals with no body symmetry for example, sponges.
Describe everything about radially symmetrical animals and give an example.
Are animals that can be divided into similar halves by passing a plane through the central axis. They have the ability to sense from all directions. Mostly posses simple nerve network with no centralized sensing or .processing. Examples are cnidarians ( hydra and jellyfish) and echinoderm (sea urchin, star fish) as adults.
Describe everything about bilaterally symmetrical animals.
Are animals that can be divided into two matching halves by passing a plane through the central axis, creating left and right sides.
Which part is favoured by natural selection in bilaterally symmetrical animals, and why?
The head end, because they come first in contact with food and danger. So the head end is favoured by natural selection for sensory ability centralized in the head.
