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level: 14.1 Survival and response

Questions and Answers List

level questions: 14.1 Survival and response

QuestionAnswer
Stimulus meaning- A detectable change on the internal or external environment of an organism that leads to a response in the organism
Advantage to organisms of being able to respond to stimuli- Increases chance of survival - Greater chance of reproducing having offspring, passing alleles to next gen - So always a selection pressure favoring organism with more appropriate responses
Flow diagram of eventsStimulus-receptor-coordinator-effector-response
How stimuli are detected- By receptors - They are specific to one type of stimulus
Coordinator- A coordinator formulates a suitable response to a stimulus - Coordination may be at the molecular level or involve a large organ such as a brain
Effectors- A response is produced by an effector - This response may be at the molecular level or involve the behavior of a whole organism - One means of communication in large, multicellular organisms occurs via chemicals called hormones, which is a relatively slow process in animals and plants - Or the nervous system
The nervous system- Usually have many different receptors and control effectors - Each receptor and effector is linked to a central coordinator - The coordinator acts like a switchboard, connecting info. from each receptor with the appropriate effector
Taxes meaning- Directional response - Organism moes its whole body either towards a favorable stimulus or away from the unfavorable one - Towards the stimulus (positive taxes) or away from the stimulus (negative taxes) and also by the nature of the stimulus
How taxes increases chance of survival- Positive phototaxis - faster rate of photosynthesis - produce more glucose - Positive chemotaxis - respiration - Negative phototaxis - reduce water loss, avoid predators
Kineses- Random movement due to an adverse stimulus - Frequency of turning is proportional to the strength of the stimulus e.g. woodlice in light
How kineses increases chance of survival- Woodlice lose water from their bodies in dry conditions - When they move from damp area into dry one , they move more rapidly and change direction more often - This increase chance of moving back into damp area
Tropisms- Diectional response to stimuli involving growth - Plant part grows towards (positive response) or away (negative response) to the stimulus
How tropisms increases chance of survival- Plant shoots grow towards light (positive phototropism) and away from gravity (negative phototropism) to maximise light absob. ] - Plant roots grow away from light (negative phototropism) and towards gravity (positive phototropism) ab. water + mineral ions