IBDP Biology - Specification

In this IBDP Biology topic , you can learn more about the ecosystem.

• Any group of living organisms and non- living things occurring together, and the interrelationships between them, can be thought of as an ecosystem
• Ecosystems are dynamic because they’re changing all the time e.g., populations of different species

• Feeding of herbivores on plants
• Predation
• Parasitism- a parasite does harm to the host
• Mutualism- two organisms have a relationship beneficial to them both

• Non-living factors such as temperature, oxygen concentration and light intensity

Producer: an organism that produces organic molecules using sunlight, e.g., plants

Consumer: An organism that eats other organisms e.g., herbivore/ carnivore

Decomposer: An organism that breaks down dead or undigested organic material, e.g., bacteria and fungi

Trophic level: A stage in the food chain occupied by a particular group of organisms e.g., producers are the first trophic level in a food chain

1. Energy enters an ecosystem, mainly, when plants photosynthesis.
2. During photosynthesis, plants convert sunlight energy into carbohydrates, proteins and fats
3.  Energy is transferred when one organism eats another
4. Food chains, pyramids and webs show how energy is transferred through an ecosystem
5. Energy in things that can’t be eaten, e.g., faeces are recycled back into the ecosystem by decomposers

Some farming methods can increase productivity by increasing energy transfer

• Herbicides kill weeds that compete with agricultural crops for energy, less competition means these crops grow faster and larger increasing productivity
• Fungicides kill fungal infections that damage crops meaning the plants use less energy fighting infection and more energy growing, increasing productivity
• Insecticides kill insects that eat the crops meaning less biomass is lost
• Natural predators (e.g., ladybirds) are introduced to eat pests and less biomass is lost
• Fertilizers provide minerals needed for growth so that this isn’t a limiting factor
• Animals can be kept warm indoors with restricted movement so less energy is used to keep them warm/ move around
• Animals may be fed higher energy food so more food is available for growth
• More food can be produced in less time but there are ethical issues such as causing animals distress

• Primary succession starts when a species colonizes a new land surface (no organic matter present) the first species to colonize this area are pioneer species and this is the first seral stage
•   The abiotic conditions are harsh, e.g., no soil to retain water, so pioneer species are specialized   to grow here. e.g., marram grass grows near the sea and can tolerate salty conditions.
•   The pioneer species die and decompose into soil, thus, changing the abiotic conditions
•   This makes conditions less hostile so new organisms can survive here and more habitats are  created

• secondary succession happens in the same way but soil (organic matter) is already present so the pioneer species are larger shrubs
• At each stage different organisms out compete less well-adapted ones
• As succession continues, the ecosystem becomes more complex and species diversity increases
• The amount of biomass also increases as plants get larger and more dense e.g., tree
• The final seral stage is a climax community- the ecosystem is supporting the largest and most complex community of organisms it can- it wont change any more and is in a stable state

This is the end of the topic

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Drafted by Eva (Biology)

Photo references:

1. https://kids.britannica.com/students/assembly/view/235362
2. https://onlinesciencenotes.com/trophic-levels-and-ecological-pyramids/
3. https://ib.bioninja.com.au/options/option-c-ecology-and-conser/c2-communities-and-ecosyste/primary-succession.html
4. https://ib.bioninja.com.au/options/option-c-ecology-and-conser/c2-communities-and-ecosyste/ecological-disturbance.html