Size and Surface Area
- Created by: jessicawarren
- Created on: 25-04-16 11:45
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- Size and Surface Area
- Exchange substances
- Cells need to take in oxygen for aerobic respiration and nutrients
- Need to excrete waste products like carbon dioxide/urea
- Most organisms need to stay at roughly same temperature, heat needs to be exchanged
- SA:V Ratio
- Smaller animals have high SA:V ratio
- Volume= L x W x H
- SA= Area of each side added up
- Always :1, simplify down
- Exchange organs/ Mass transport systems
- Organism needs to supply every one of its cells with glucose/oxygen for respiration
- Also needs to remove waste products
- Single celled organisms- substances diffuse directly across CSM. Diffusion rate quicker, shorter diffusion distance
- Multicellular- diffusion too slow: Long diffusion distance, low SA:V ratio (can't supply enough substances for whole organism)
- Multicellular animals need specialised exchange organs
- Also need mass transport systems e.g circulatory, blood carries glucose/oxygen/hormones/antibodies/waste. Plants use xylem/phloem
- Heat exchange
- Rate of heat loss depends on SA
- Small SA= less heat loss. Large SA= more heat loss
- Smaller organisms need high metabolic rate to generate heat
- Animals with compact shape have smaller SA, minimises heat loss
- Less compact shape means larger SA, increases heat loss
- Temp of animals environment determines shape: Arctic fox compact, African bat eared fox not, European fox in between
- Behavioural/ Physiological adaptations
- Animals w/ high SA:V ratio lose more water by evaporation from surface. Small desert mammals have kidney adaptation, produce less urine
- Small mammals in cold regions eat high energy foods to support high metabolic rate
- Smaller mammals have thick fur/hibernate in cold weather
- Larger organisms in hot regions- Elephants have large, flat ears to increase SA, lose more heat. Hippos spend large part of day in water to keep cool
- Exchange substances
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