Interactions Within Ecosystems

Date: ______

P. _____ in ILL

Ecology—the scientific study of interactions between different organisms their environment

An ecologist would study organisms that live in an ecosystem. Ecosystems are a network of living and non-living things that interact. The size of the ecosystem depends on the shared similarities between living and non-living things—can be small or very large.

Biotic—living factors that influence an ecosystem

Abiotic—non-living factors that influence an ecosystem

Who makes up an ecosystem?

• Organisms within an ecosystem are classified into: –Individuals—singular organisms

–Populations—all the individuals that belong to one species in a habitat

–Communities—all the combined populations in a habitat

• Ecological Niche – an organism’s role in an ecosystem. This includes its: place in the food web, habitat (home), breeding area, etc.

• Within ecosystems, each organism has its own specific niche. No two species fulfill exactly the same role.

Example: The ecological niche of a sunflower growing in a backyard includes: absorbing light, water and nutrients (for photosynthesis), providing shelter and food for other organisms (e.g. bees, ants, etc.), and giving off oxygen into the atmosphere.

• If a new, exotic species is introduced into an ecosystem, it will have to compete with any species that is already fulfilling the same niche the new species would. Eventually, one of the two species will be out-competed and cannot survive in the ecosystem. During this process, the entire ecosystem will be disrupted.

Limiting Factors are… • Environmental conditions that may prevent

populations from reaching their biotic potential. This means that the ecosystem could sustain more members if the limiting factor was not there.

• Limiting factors may be biotic or abiotic

Limiting Factors cont…

ABIOTIC FACTORS • too much or too little light

• temperature too cold or too warm

• harmful chemicals in the environment

BIOTIC FACTORS • insufficient food

• excessive predators

• diseases or parasites

• diminished ability to compete with other species

Carrying Capacity

• Is the maximum number of individuals of a single species that can be supported in an ecosystem at a particular time. This is determined by the availability of food, presence of predators, disease and other resources. If a population exceeds the carrying capacity, there will be a decline in number until the population re-stabilizes.

Abiotic factors will often determine the number of organisms that can live in an ecosystem. Two basic rules govern the effects of abiotic factors:

Law of Minimums – states that the nutrient or resource in the least supply is the one that limits growth.

• Ex. Limited water resources during a drought will determine the growth of plants

Law of Tolerance – states that organisms can only tolerate or survive within a particular range of an abiotic factor.

• Ex. tiger barb fish only live between 20 – 25°C.

Biotic factors can also determine the carrying capacity for a species in an ecosystem. These factors include:

Density dependent factors – affect populations based on the density or number of individuals present.

• Ex. disease, food supply, predators, availability of sunlight or water due to competition, and space

Density independent factors – affect members of a population regardless of the number of individuals present.

• Ex. fire, flood, drought, chemicals, pollution, climate change and other natural disasters

Sustaining Ecosystems

• Ecosystems are destined to change, gradually, over time. Sadly, human induced changes often leave ecosystems unable to replenish resources and the delicate balance of life is upset. Terrestrial and aquatic ecosystems each have a unique set of limiting factors and challenges that threaten their sustainability.

Terrestrial Ecosystems • Terrestrial ecosystems are limited by four major abiotic

factors:

1. Soil: Provides nutrients for all plants that grow on land. Poor quality soil is an important limiting factor in many ecosystems

2. Available Water: Since water is essential to all life water can easily become a limiting factor for a population. Plants are able to adapt to changing availability of water by directing their roots deeper underground to reach groundwater during droughts or periods of low precipitation.

3. Temperature: Many plants and animals adapt to a specific range of seasonal temperatures. A variety of strategies such as hibernation, migration, shedding leaves, a winter coat and dormancy are used to help these organisms survive.

4. Sunlight: has an effect on all terrestrial ecosystems. The amount of sunlight usually varies with the geographical location and with the canopy plants that are growing in a specific area.

Aquatic Ecosystems

• Aquatic ecosystems are often very diverse and are important to the earth’s ecological state. These ecosystems are affected by three major abiotic factors:

– chemical environment (level of dissolved oxygen)

– light levels (this is the most important abiotic factor)

– Water temperature

Relationships within an Ecosystem

Interdependence

What is interdependence? • There are several different complex

relationships that exist among organisms in an ecosystem. Organisms can be interdependent, meaning their population size or lives would be greatly affected without the other’s presence. Relationships like predation and mutualism can help to regulate populations.

Symbiosis—any relationship between two species that live in the same ecosystem.

1. Mutualism—both species benefit (WIN-WIN)

a. Ex: insects and flowers the insects get food and the flowers could not pollinate and reproduce without the insects help

Can you think of any other examples?

2. Commensalism—one member of the relationship benefits and the other is neither helped nor harmed.

(WIN-0) Example: barnacles on a whale

the barnacles have a place to live and the whale is not harmed or

helped by their presence

3. Parasitism—one organisms lives on or inside another organism (the host) and harms it.

The parasite obtains all or part of its nutritional needs from the host. (WIN-LOSE)

Example: fleas on a dog the fleas depend on the dog to survive, the dog is harmed by their presence

Predation—one organism captures and feeds on another organism

1. Predator—one that does the killing

2. Prey—one that is the food

Who wants to be in a symbiotic relationship? For the next 6 slides determine whether the relationships shown are mutualism, commensalism, parasitism, or predation.

Parasitism

Mutualism

Lobster and Sea Turtle– the sea

turtle is about to eat the lobster as

crunchy little snack!

Rhino and Oxpeckers—Oxpeckers (also

known as tickbird) will feed off ticks,

horsefly larvae and other parasites in the

rhino’s ears.

Aerophytes (epiphytes)—plants that grow

high up on another plant to obtain nutrients

and moisture from the air but cause no

harm to that plant

Shark and Remora—the remora fish will

attach to the shark, get a free ride and feed

off scraps left behind as it eats or that get

dropped as it tears the flesh from its prey

Female mosquito biting a human—

mosquito will feed off the blood and the

human will be harmed.

Ant, Acacia and Caterpillar-The caterpillars

have nectar organs which the ants drink

from, and the acacia tolerates the feeding

caterpillars. The ants appear to provide

some protection for both plant and

caterpillar.-

Ecological Interactions Between Organisms Competition—when two organisms of the same or different

species attempt to use an ecological resource in the same place at the same time.

Ex: food, water, shelter, mates

Cooperation—necessary to provide for young, escape predators, and protect/ preserve the territory

Cooperation among competitors promotes coexistence

Monkeys compete with each other and other animals for food.

Rams compete with each other for mates.

Energy Flow Through an Ecosystem

Food Chains, Food Webs, Energy Pyramids

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Nearly all of Earth’s energy begins with the sun!

• Sunlight is necessary for organisms to produce their own energy.

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Organisms that make their own energy (glucose) during photosynthesis are called PRODUCERS.

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Producers use most of the energy they make for themselves for cellular respiration which releases the energy needed for all life processes.

Photosynthesis •Chemical reaction in chloroplasts of producers that uses energy from the sun to transform water and carbon dioxide into glucose and oxygen

•ENERGY is stored in glucose

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CELLULAR RESPIRATION Chemical reaction in the mitochondria of all cells to convert glucose and oxygen into usable energy that allows organisms perform the necessary life processes.

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6O2 + C6H12O6 6H2O + 6CO2 + energy

It’s a cycle! The O2—CO2 cycle or photosynthesis/ respiration cycle.

The energy that is not used by producers can be passed on to organisms that cannot make their own energy.

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Consumers that eat producers to get energy…

•Are first order (1st)/trophic level or primary consumers

•Must be herbivores (plant-eaters) or omnivores (plant and meat eaters)

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Organisms that cannot make their own energy are called CONSUMERS.

Most of the energy the primary

consumer gets from the producer is used by the consumer.

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Some of the energy moves into the atmosphere as heat.

Some energy in the primary consumer is STORED & not lost to the atmosphere or used by the consumer itself.

This energy is available for another

consumer (predator).

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A Consumer that Eats Another Consumer for Energy:

•Is called a secondary or 2nd order consumer

•May be a carnivore or a omnivore

•May be a predator

•May be a scavenger

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Most of the energy the secondary consumer gets from the primary consumer is used by the secondary consumer.

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Some of the energy is lost as heat, but some energy is stored and can passed on to another consumer.

A consumer that eats a consumer that already ate a consumer:

•Is called a 3rd order or tertiary consumer

•May be a carnivore or a omnivore

•May be a predator

•May be a scavenger

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Consumers that eat other dead consumers are called

scavengers

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All dead and decaying matter at each trophic level is broken down by decomposers such as bacteria and fungi. The recycling of raw materials and nutrients back into the soil after decomposition—a process call biodegradation, is vital to all ecosystems. 47

The transfer of energy from the sun to producer to primary consumer then to higher order consumers can be shown in a FOOD CHAIN.

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Another way of showing the transfer of energy in an ecosystem is the ENERGY PYRAMID

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Energy Pyramids Show •Amount of available energy decreases for higher order consumers

•It takes a large number of producers to support a small number of primary consumers

•It takes a large number of primary consumers to support a small number of secondary consumers

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Remember: Every chemical process that happens in your body releases heat as a byproduct (ex: burning calories).

Rule of 10—only about 10% of the available energy within a trophic level is transferred to the next higher trophic level

Biomass Pyramid—represents the amount of living organic matter at each trophic level

Energy Pyramid Biomass Pyramid

100%

10%

1%

0.1%

Food Webs:

•Are interconnected food chains

•They show the feeding relationships in an ecosystem

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Identify the Producers, Consumers, & Decomposers:

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Count the

Food

Chains!