Higher Level Ecology Syllabus links Pyramid of Numbers
Higher Level Ecology
Syllabus links
Pyramid of Numbers Fox Rabbit Grass What 2 inferences can be drawn from the normal shape of a pyramid of numbers?
Limitations of pyramids of numbers What do pyramids of numbers not take into account? Inverted Pyramids of Numbers
Factors that control Population 1. 2. 3. 4. Competition Predation Parasitism Symbiosis These factors help maintain a balance in the population called the Balance of Nature
Competition � � � Competition occurs when organisms actively struggle for a resource that is in short supply. Plants compete for space, light, water and minerals Animals compete for food, water, shelter, territory and mating rights
� Intra-specific competition: Between members of the same species � Inter-specific competition: Between members of different species
2 types of Competition 1. Contest Competition: An active physical contest between two organisms which results in one winning the resource. E. g. Deer 2. Scramble Competition: All of the competing individuals get some of the resource. E. g. Ivy and Hawthorn tree compete for available light.
� � Species should avoid competition to survive. Must adapt to their environment by either feeding habits, camouflage, protective coats, Reproductive strategies. E. g. The Kangaroo can carry up to 3 offspring 1. Joey 2. New born baby (size of your baby finger) 3. Fertilized Egg sitting in tubes to go to womb
Predation � � This is the catching, killing and eating of another organism. Predation has positive effects on an ecosystem 1. 2. 3. Predation stabilises the community Predators control the number of herbivores and so prevent overgrazing. Predators eliminate the less adapted/weaker prey
Adaptations of Predators and Prey 3 Adaptation of Predators 1. Hawks have excellent eye sight 2. Ladybirds have strong mouth parts 3. Cheetahs can run at 60 km/hr 3 Adaptation of Prey 1. Frogs are well camouflaged. 2. Zebras have strips, when in a group lions can’t distinguish where one ends & another begins. 3. Ladybirds contain large amounts of Formic acid so they are unpalatable to taste.
Parasitism � This occurs when one organism, the Parasite, benefits from another organism , the Host, by obtaining food from it and harming it in the process. � The parasite either lives 1. On the Host (Exoparasites) – Flea 2. In the Host (Endoparasites) – Liver Fluke
Symbiosis � � � Occurs when 2 organisms of different species live in close association and at least 1 of them benefits. Parasitism is a form of symbiosis. Where both organisms benefit is called Mutualism E. g. Nitrogen-Fixing Bacteria on nodules of plants. Bacteria in large intestine of humans produce vitamin B and K.
Population Dynamics 1. 2. 3. The numbers of predators and prey are inter-related The variables that contribute to predatorprey interactions include: Availability of food Concealment Movement of predators
Factors that contribute to Predator-Prey interactions 1. 2. 3. Availability of Food Large no. of antelope will increase no. of Lions. This will decrease no. of antelope and then Lions. When lions decrease antelope will increase again. Concealment When there are less prey they can hide better, this allows population of prey to survive and increase. Movement of Predators If there is not enough prey, predator moves to area with more prey.
Human Population Growth
� � Human population 500 million in 1650 2 billion in the early 1930 s 4 billion in 1970 s Passed 6 billion in 2000 Population increasing by 85 million a year Equal to 230, 000 people each day or 160 every minute 66% of the worlds population live in Asia Increase in population is caused by decrease in death rates
Factors Affecting Human Population Numbers � Wars reduce population but effects are temporary as baby booms often follow after wars � Famine Lack of food leads to malnutrition and death. Occurred in Ireland 1845 -1847, 1 million people died.
� Contraception Increased availability has reduced birth rates Developed countries average no. of children born to a women is 2. 1. Developing countries average no. of children born to a women in 1970 s was 6. 1 Today it is about 3. 5 � Disease Improved disease control methods have reduced the death rate and caused an increase in human numbers
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