population growth limiting factors interspecific competition intraspecific competition predation
TRANSCRIPT
Why do populations vary in size?
•Population growth•Limiting factors •Interspecific competition• Intraspecific competition• Predation
Slow growth Rapid Stable state – no growth
Population growth curves
Small fluctuations due to changes in factors such as food supply.
The growth of a population is slowed by limiting factors.
Imagine a single celled Algae living in a new pond in summer, the algae divides rapidly at first as there are no limiting factors. What will slow the algal growth?
Lack of mineral ions Algae at the surface prevent light reaching
algae further down. Other species – competition or predators Winter – lower temperatures or light intensity
Limiting factors
Abiotic Temperature: each species has an optimum
temperature.Below, the metabolic rate drops.Above, enzymes denature.Even animals that can maintain a relatively
constant temperature will be affected by temperature as they will expend more energy trying to maintain their normal body temperature. So they mature and reproduce slower.
Limiting factors
Abiotic LightThe rate of photosynthesis increases as the
light intensity does. Therefore more plants grow and more animals can be fed.
Water and humidityLack of water results in a small population of
animals adapted to dry conditions. Humidity affects plant transpiration rates and
evaporation of water from animals bodies.
Limiting factors
Why do populations never grow indefinitely?
What is the difference between biotic and abiotic factors?
Suggest the level and type of abiotic factor that is most likely to limit the population size of the organisms:
a. Ground plants on a forest floorb. Hares in a sandy desert.c. Bacteria on a high mountain summit.
Questions
Where would only the blue species be found?
Where would moisture and temperature allow both species to live?
The temperature too high for the blue’s?
There is competition between the 2?
Application
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Competition between members of the same species.
Competing for food, water, breeding sites etc.
Availability of resources determines the size of the population.
Examples?
Intraspecific competition
Competition between members of different species.
Where 2 species occupy the same niche one may have a competitive advantage and will increase in size while the other diminishes. This can lead to the complete removal of a species = the competitive exclusion principle. No two species can occupy the same niche indefinitely when resources are limiting.
Interspecific competition
When cultured in isolation, the population density of each species of Paramecium increases rapidly and then levels off
In mixed culture, competition for food, space and other minerals results in the elimination of Paramecium caudatum after about 20 days; the more rapidly
reproducing Paramecium aurelia outcompetes its rival
Predator and Prey
An organism’s niche includes how it avoids being eaten and how it finds or captures its food. Predators are
consumers that capture and eat other consumers. The prey is the organism that is captured by the
predator. http://www.bbc.co.uk/nature/adaptations/Predation#p00g9r9k
Niches and barnacles
Balanus balanoides
chthamalus stellatus
Predator and Prey
The deer is being eaten by the python. It is prey.
The python has captured and is eating the deer.
Predator and Prey
Predator
Prey
Predator and Prey
PredatorPrey
Predator and Prey
Prey Predator
Predator and Prey
This alligator is the predator. It eats the python.
This python is the prey. It is eaten by the alligator.
Lynx vs. Hare
Predator/Prey Relationship
Predator/Prey Relationship
The presence of predators usually increases the number of different species that can live in an ecosystem. Predators limit
the size of prey populations. As a result, food and other
resources are less likely to become scarce, and competition
between species is reduced.
Predator/Prey Relationship