Lesson 2: Symbiosis & Nutrient cycles

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Ecology

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Learning objectives

• Describe how different factors influence population size
• Identify different types of symbiosis and describe advantages and disadvantages for individual organisms
• Describe that path carbon and nitrogen take in their respective cycles

What is a population?

With reference to the following statements about a woodland ecosystem. Which statement describes a population?

1. All the oak trees
2. All the plants
3. All the plants and animals

Population size

immigration

emigration

death

birth

Population growth

Involves:

1. Biotic potential: max reproduction rate given all the resources the population needs
2. Environmental resistance: all factors that may limit growth. (scarcity of resources, predation, climate conditions etc)
3. Carrying capacity: max population size that can be supported by a particular environment

Population curves

• J-curve: often seen in fast reproducing organisms that colonise a new environment. Exponential growth followed by hitting a limiting factor and often the population crashes
• S-curve: Exponential growth until population hits environmental resistance and stabilises around the carrying capacity

Carrying capacity

Environmental resistance

Few reproducing individuals

Exponential growth

What is population density?

Environmental resistance

Can be:

• Density indepent: these factors influence all organism in a population irrespective of population density. Can be biotic of abiotic
• Density dependent: the influence of these factors on population size depend on the density of the population. Usually the higher the density the bigger the impact of these factors. Always biotic

Density independent

Density dependent

Light

parasitism

earthquake

competition

disease

A factor that would increase the size of the population

1. Emmigration
2. Death Rate higher than Birth Rate
3. Birth Rate Higher than Death Rate
4. Drought

A factor that is more likely to affect crowded population much more than spread out population

1. Density dependent factor
2. Limiting factor
3. Natural disaster
4. Density independent factor

A factor that decreases the population or keeps it from increasing

1. Limiting factor
2. Food surplus
3. High birth rate
4. Carrying capacity

Example of a density independent factor

1. Natural Disaster
2. Disease
3. Resource Availability/Competition
4. Predators

What is the carrying capacity of the following graph?

1. Around 500
2. More than 500
3. Less than 500
4. Around 600

02:27

All of the following statements concerning characteristics of predator-prey relationships are
correct EXCEPT:

1. A rise in the population of prey is often followed by a rise in the population of predators.
2. A rise in the population of predators is followed by a decrease in the population of prey.
3. The production of large numbers of offspring within very short periods of time ensures the survival of some prey populations.
4. The population of predators most often eliminates the population of prey.

03:29

Intra means within

Inter means between

Intraspecific competition

Interspecific competition

What does symbiosis mean?

1. living separately, no relationship between 2 species
2. living together, close relationship between 2 species
3. living in a community with no interaction between each other
4. living together in fear of each other

Ants and acacia trees have a mutualistic relationship because:

1. They both benefit from living with each other.
2. They are part of the same ecosystem.
3. They are both adapted to a humid climate.
4. The ants eat part of the acacia tree.

Which of the following symbiotic relationships is considered parasitic?

1. Bees transporting pollen from flowers
2. Pilot fish swimming under sharks
3. Birds eating the insects from the back of a hippopotamus
4. Tapeworm in an intestinal tract

Explain and define what type of relationship this is and give 2 examples of why it is that symbiotic relationship by discussing how each individual organism is directly
affected by the other organism. Provide another example of organisms sharing the same symbiotic relationship as the hummingbird and flower.

Plants transform energy from the sun into:

1. nuclear energy
2. solar energy
3. chemical energy
4. mechanical energy

If the decomposers were removed from an ecosystem, what would most likely occur?

1. Energy from the sun would not be absorbed by plants
2. Carnivores would have no source of energy
3. Essential elements would not be available to plants
4. Herbivores would lose their source of energy and nutrients

Use the food chain below to answer the next question.

Grass → Prairie dog → Rattlesnake → Hawk

What sequence below best represents how much energy is passed from one organism to the next in the food chain above?

1. 100% → 10% → 1% → 0.1%
2. 100% → 50% → 25% → 12.5%
3. 100% → 75% → 50% → 25%
4. 100% → 90% → 80% → 70%

03:57

Photosynthesis

Animal respiration

Plant respiration

Fossil fuels

Atmospheric nitrogen (N2)

Denitrifying bacteria

Nitrifying bacteria

Ammonium (NH4+

In an environment, elements such as carbon are usually

1. converted into nuclear energy
2. synthesized and remain as fossil fuels
3. converted into nonrenewable resources
4. recycled and reused by other organisms

Which of the following statements is NOT true about this diagram?

1. Carbon dioxide and oxygen are used by producers in the ecosystem
2. Living organisms remove and replace oxygen back into the atmosphere.
3. Consumers generate oxygen and consume carbon dioxide
4. Living organisms generate carbon dioxide which is used by other organisms

Would you say that the transfer of energy through the ecosystem was a cyclical
process where the energy is reused or a flow in one direction?
Give reasons for your choice.

Organic farmers do not use artificial fertilisers to put nitrates into the soil.
Explain why organic farmers often keep farm animals, even if they mainly grow crops such as wheat.

Homework

Worksheet Symbiosis & Nutrient cycles