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Flashcards in Communication and Homeostasis Deck (45)
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Explain why multicellular organisms need a communication system.

Cells within organisms have become specialized to perform specific functions. Organisms need to coordinate the function of different cells and systems in order to operate effectively and respond to changes in their environment. Few body systems can work in isolation.


List the factors that need keeping constant inside cells.

- blood glucose concentration
- internal temperature
- water potential
- cell PH


Explain why it is important to keep conditions inside cells relatively constant.

Keeping your internal environment constant is vital for cells to function normally and stop them being damaged e.g. optimum temperature and PH for enzyme activity + maintaining a concentration of glucose in the blood so that there is enough for respiration.


Explain why the conditions critical to an organism change (use 4 examples from the internal environment and 4 examples from the external environment).

- blood glucose conc
- internal temp
- cell ph
- water potential

- humidity
- external temperature
- light intensity
- new or sudden sound

The conditions change because substances are used up in metabolic reactions, waste products are constantly being produced, metabolisms change to meet changing demands of the organism, intake varies over time and environmental conditions change.


Name the process by which cells communicate with each other.

Cell signalling


Define the term “cell signalling”.

Inter-cellular communication wherein one cell releases a chemical which has an effect on another cell, known as the target cell.


Give two examples of systems whose purpose is cell signalling.

- nervous system
- endocrine system


Outline the process of cell signalling in the nervous and endocrine systems.

Nervous system -
signals are transferred locally between neurones at synapses. Here the signal is used as a neurotransmitter.

Endocrine system -
transfer signals across large distances, using hormones. e.g. the pituitary gland, secreting anti-diuretic hormones.


Compare the neuronal and hormonal systems of cell signalling.

Hormonal system:
- communication by chemicals (hormones)
- transmission by blood stream
- relatively slow transmission
- hormones travel to all parts of the body but only target organs respond
- response is slow but widespread
- response is long-lasting
- effect may be permanent + irreversible

Nervous system:
- communication by nerve impulses
- transmission by neurones
- transmission v. quick
- nerve impulses travel to specific parts of the body.
- response is rapid
- response is localised
- response is short-lived
- effect is temporary and reversible


Define the term “negative feedback”.

Negative feedback is a mechanism whereby a change away from the ideal triggers a reaction to bring the conditions back to ideal.


Define the term "positive feedback".

In the positive feedback mechanism, a change in the internal environment of body is detected by sensory receptors, and effectors are stimulated to reinforce that change and increase the response.


List 4 factors that need to be kept constant (within a narrow range) in animals.

- PH of the blood
- core body temperature
- concentrations of urea and sodium ions in the blood


Define homeostasis.

The maintenance of a stable equilibrium in the conditions inside the body.


Draw a flow chart to outline the processes (and components) involved in negative feedback.

1) Change away from optimum/ norm
2) this change is detected by receptors
3) Signals are sent to effectors, sometimes via a control centre
4) effectors initiate a response
5) conditions return to optimum/ norm


Define the terms “effector” and “receptor” in relation to negative feedback.

effector -
muscle or gland which carries out the body's response to a stimulus
receptor -
extrinsic glyco-proteins that bind chemical signals, triggering a response by the cell (they detect changes in the internal and external environment of an organism)


Explain what is meant by “constant” in terms of homeostasis.

Maintaining a relatively steady state around a narrow range of conditions.


Define the terms “endotherm”.

Endotherms - animals that rely on their metabolic processes to warm their bodies and maintain their core temp.


Define the terms “ectotherm”.

Ectotherms - animals that use their surrounding that warm their bodies so their core temp is heavily dependent on the environment.


Define the term “thermoregulation”.

Thermoregulation is the maintenance of a relatively constant core temp.


Define the term “core body temperature”.

The temperature of the internal environment of the body.


Explain why “warm-blooded” and “cold-blooded” are inappropriate terms for endotherms and ectotherms.

Because blood is never cold (unless you're dead).


Explain why temperature needs to be maintained within a narrow range with cells.

Because enzymes controlling chemical reactions needed for life are very temperature sensitive. If temp gets too high they will denature.


Describe and explain 4 ways that heat is transferred between an organism and their environment.

- Exothermic chemical reactions
- Latent heat of evaporation:
objects cool down as water evaporates from a surface.
- Radiation:
the transmission of electromagnetic waves to and from the air, water or ground.
- Convection:
heating or cooling by currents of air or water.
- Conduction:
heating as a result of the collision of molecules.


Describe how an organism generates heat internally.

- from metabolic process
- the metabolic rate of endotherms is much higher than ectotherms.


Define the term “exothermic reaction”.

- reactions that release energy


Describe the advantages and disadvantages of being an ectotherm. (F)

- core body temp is heavily dependent on their environment
- temperature of air can vary dramatically, meaning land ectotherms have a big problem with maintaining temp.7
- restricted to tropical or temperate regions.
- many ectotherms living in water don't need to thermoregulate because the high specific heat capacity of water means the temp of water does not change that much.
- their metabolic demands are much lower, so less food is needed.
- activity levels are severely reduced when it is cold and they may be completely inactive during winter
- more of the food eaten can be used for growth


Outline how an ectotherm regulates its internal temperature (BEHAVIOURAL)

- bask in the sun/ orientate their bodies so that the maximum surface area is exposed to the sun.
- some extend areas of their bodies to increase SA
- increase body temp by conduction by pressing their bodies against warm ground.
- exothermic reactions, contracting muscles and vibrating to increase cellular metabolism and raise body temp.

- shelted in shade/ dig burrows
- press bodies against cool earth
- move to available mud/water
- activity minimised to reduce metabolic heat generated.


Outline how an ectotherm regulates its internal temperature (PHYSIOLOGICAL)

- dark colours absorb more radiation than light colours so lizards living in colder climates tend to be darker skinned.
- alter heart rate to increase or decrease the metabolic rate


Draw a table to show 6 adaptations for temperature regulation in ectotherms, and how they help regulate temperature. Give an example for each adaptation.



List 4 different types of organism that are ectotherms.

- all invertebrate animals including:
- fish
- amphibians
- reptiles