Rhythms
What is a biological rhythm?
A repeating pattern of biological activity over time.
A plant's roots grow towards an area of higher moisture in the soil. What orientation response is this?
Positive hydrotropism
What is photoperiodism?
A plant's response to the relative lengths of light and darkness.
What is commensalism?
When one organism benefits and the other is unaffected.
What reproductive strategy involves producing many offspring with little parental investment?
R-selected strategy
What type of rhythm has a period of approximately 24 hours?
Circadian rhythm
What navigation methods can sharks use during long-distance migration?
Earth's magnetic field via magnetoreception and chemical navigation
What is the difference between a long-day plant and a short-day plant?
Long-day plants flower when day length exceeds their critical day length (short night).
Short-day plants flower when day length is shorter than their critical day length (long night).
What are the three types of exploitation?
Predation, herbivory, parasitism
Give one purpose of courtship
Species recognition, mate choice, reducing aggression or synchronising reproduction
What is the difference between an endogenous and exogenous rhythm?
Endogenous = internally controlled; exogenous = controlled by external environmental cues.
What is taxis, and how is it different from kinesis?
Taxis is directional movement towards or away from a stimulus
Kinesis is a non-directional change in movement or activity in response to stimulus intensity.
At night, what happens to phytochrome?
Pfr is slowly converted to Pr
What does a symbiotic relationship describe?
A close, long-term relationship between two different species.
e.g. mutualism, commensalism, parasitism
What is the difference between agonistic and aggressive behaviour?
Agonistic is the broader category of conflict-related behaviour.
Aggressive behaviour involves actively threatening or attacking.
An animal's activity occurs slightly earlier each day in constant darkness. What does this tell you about its endogenous period?
It is less than 24 hours.
A flatworm moves into a brightly lit area. It increases its frequency of turning. When it reaches a darker area, its turning frequency decreases.
Identify the response and explain how it provides an adaptive advantage.
Klinokinesis — increased turning helps the flatworm leave unfavourable bright areas and remain in favourable dark conditions, increasing survival.
Why is photoperiodism useful to plants?
It allows plants to use predictable changes in day/night length to time flowering when environmental conditions are favourable for reproduction.
Why is interspecific competition described as
−/−?
Both species are negatively affected because each reduces the other's access to a limited resource.
A group of animals has a strict hierarchy. Explain one benefit of this hierarchy.
It reduces repeated conflict and injury because individuals know their rank, saving energy and helping organise access to resources
What is the difference between a zeitgeber and entrainment?
A zeitgeber is the environmental cue that resets the biological clock, while entrainment is the process of synchronising the biological rhythm with that cue.
How does positive phototropism work?
Light from one side causes auxin to accumulate on the shaded side, leading to greater cell elongation and bending the shoot toward the light.
A short-day plant normally flowers after a long, uninterrupted night, but if it receives a brief red-light flash during a long night, it does not flower. Explain why.
The red light rapidly converts Pr to Pfr, interrupting the long-night signal required for flowering.
Antibiosis and allelopathy — both involve chemical release
Antibiosis is by bacteria/fungi, while allelopathy is by plants.
Why might high resource density result in smaller territories?
More resources are available in a smaller area, so less space needs defending.