Interactions Between Organisms and Adaptations


Organisms compete to survive

In order to survive and reproduce, organisms must compete against each other for the resources that they need to live. 

Similar organisms in the same habitat will be in the closest competition because theyll be competing for similar ecologial niches
A ecologial niche is how it fits into its ecosystem. It depends on things like where they live and what they feed on.

Two types of competition between organisms:

  • INTERSPECIFIC COMPETITION is where organisms compete for resources against individuals of another species. 
  • INTRASPECIFIC COMPETITION is where organisms compete for resources against individuals of the same species

Intraspecific competition has a bigger impact on organisms than interspecific competition, beause same species have exactly the same needs, so theyll compete for lots of resources.

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Parasitic and Mutualistic Relationships

Parasites live off a host. They take what they need to survive, without giving anything back. This often harms the host which makes it a win lose situation. 

  • Tapeworms absorb lots of nutrients from the host, causing them to suffer from malnutrition
  • Fleas are parasites. Dogs gain nothing from having fleas.

Mutualism is a relationship where both organisms benefit, so its a win win relationship. 

  • "Cleaner species" For example oxpeckers live on the backs of buffalo. Not only do they eat pests on the buffalo, like ticks, flies and maggots, but they also alert the animal to any predators that are near by hissing. 
  • Lots of plants are pollinated by insects, allowing them to reproduce. In return, the insect gets a sip of nectar 
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1. Adaptations are the features that organisms have that make them better suited to their environment.
2. Organisms that are adapted to their environment are better able to compete for resources.
3. This means that they are more likely to survive, reproduce and pass on their adaptations to their offspring.

SPECIALISTS are organisms which are highly adapted to survive in a specific habitat.
GENERALISTS are organisms that are ada
pted to survive in a range of different habitats

In a habitat where the conditions are stable, specialists will out complete generalists as they are better adapted to the specific conditions. 

 But if the conditions change, specialists will be out completed by generalists. Specialists wont be adapted to the new conditions, but generalists are adapted to a range of conditions so they are more likely to survive.  

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Adaptations to cold

Anatomical adaptations

  • Having a thick coat or a layer of blubber to insulate the body and trap heat in
  • Having a large size and compact body shape to give a small surface area to volume ratio. This reduces heat loss as less body heat can be lost through the surface of the skin. 

Counter current heat exchange

  • Animals like penguins have to stand on cold ice all day. Blood vessels going to and from the feet carry blood that flows in the opposite direction.
  • The vessels pass close to each other, allowing heat to transfer between them.
  • Warm blood flowing in arteries to the feet heats cold blood returning to the heart in the veins.
  • This means that the feet stay cold, but stops cold blood from cooling down the rest of the body. 
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Adaptations to hot and dry

Anatomical adaptations

  • Animals in hot environments are often small. This gives them a large surface area to volume ratio which allows them to lose more body heat to their surroundings.
  • Having large ears can also increase and animals surface area to volume ratio and help them lose heat. Large thin ears allow more blood to flow near the surface of the skin so more heat from the blood can be radiated to the surroundings. 
  • Storing fat stops the rest of the body from being too well insulated and allows heat to be lost easily. 


  • Hot climate animals often spend the day in the shade or underground to minimise heat gain
  • Being active at night, when its much cooler reduces heat gain
  • Bathing in water increases heat loss. As water evaporates it transfers to heat from the skin to the surroundings. 
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1. Charles Darwin knew that organisms in species show wide variation.

2. He concluded that the organisms that are best ada
pted (fittest) would be more sucessful competitors and would more likely to surive. "Survival of the fittest"

3. Sucessful organisms that survive re
produce and pass on the adaptations that made them sucessful to their offspring.

4. Over time, sucessful adaptations become more common in the population and the species changes. It evolves.

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Theories of Evolution

1. The theory went against common religious beliefs about life on Earth developed.

2. Darwin couldnt explain why new, useful characteristics appeared or how they were inherited.

3. There wasnt enough evidence to convince many scientists, because not many other studies had been done into how organisms change over time. 


Lamarck argued that if a characteristic was used a lot by an animal then it would become more developed. He reckoned that these acquired characteristics could be passed on to the animals offspring

But people eventually concluded that aquired characteristics dont have a genetic basis. So theyre unable to be passed on to the next generation. His theory was rejected.

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