Gr 7 Interactions and Ecosystems

Topic 6: Succession and Change in Ecosystems

Succession and Change

Changes are constantly occurring in an ecosystem. Some changes are rapid (e.g. a landslide) while others changes are slow (e.g. seeds developing into plants).

Succession and Change

Succession and Change

Succession and Change

Succession is a gradual process by which some species replace other species in an ecosystem. The organisms that are present change the environment in such a way that other species can move in.

Succession and Change

Primary succession is the gradual growth of organisms in an area that was previously bare, such as rock. Occurs in uninhabited areas with no soil.

An example of primary succession would be lichens, mosses, ferns growing on bare rock. They become established and change the conditions of the area (i.e. break down rock into soil).

Primary Succession

Lichens can use chemicals to etch away the rock, leaving depressions in which soil and seeds can gather.

Primary Succession

Mosses can provide shelter for small animals and insects.

Primary Succession

Ferns are hardy plants that can live in harsh conditions.

Primary Succession

Succession can take hundreds or thousands of years.

Primary succession after the retreat of a glacier.

Secondary Succession

Secondary succession is the gradual growth of organisms in an area that previously had a number of organisms occupying it. It occurs in areas where there is already some soil on the ground and thus happens faster than primary succession.

An example of secondary succession would be the regeneration of a burnt forest area or abandoned fields.

Secondary Succession

Mechanics of Succession

Lichens: Produce acids that help break down rock. Broken-down rock and decomposed dead lichens contribute to soil formation.

Mosses and Ferns: Can grow where soil is poor and thin; they slowly replace the lichens.

Mechanics of Succession

Grass and Weeds: Soil layer thickens (can hold more water). Grass and weeds take root and attract insects, such as bee and butterflies.

• Bushes and Trees: Take root in thick rich soil. They provide shelter for birds, mammals, etc which start moving in.

Changes Caused by Human Activity

Some ways which humans can affect the environments around them are: – Human technology (in forestry and agriculture)– Spread of urban areas– Highways and parking lots– Agriculture– Extracting natural resources

Changes Caused by Human Activity

Some examples of negative aspects of when humans change the environment are: – Decrease in animal habitat– Decrease in population of some species– Animals may move to urban areas and be a

“nuisance” (i.e. cougars)– Trees are cut down which means less oxygen and

more carbon dioxide

Changes Caused by Human Activity

Some examples of positive aspects of when humans change the environment are: – The humans benefit – we get what we need/want– Provide new habitat for some animals (i.e.

National parks)– Cut down trees thereby allowing new things to

grow

Some Species Adapt Better Than Others

Give an example of when one species are more adaptive to others:

The coyote is better able to adapt to urban areas than wolves.

Some Species Adapt Better Than Others

Give an example of when one species are more adaptive to others:

The cowbirds adapt faster than their neighbours to newly cleared land and their population is on the rise.

Some Species Adapt Better Than Others

The cowbird, like the cuckoo, lays its egg in the nests of other birds. The chick hatches sooner than most others types and is large and noisy. It will often squeeze out the other chicks in an effort to get fed.

Changes Caused by Human Activity

How is it possible for pest control to actually increase the population of pests? Pesticides harm the insects that normally prey on the pests, so as their predator population decreases, the pest population actually increases. Pesticides can also kill unintended species as well: poison that kills the lygus bug also kills bees.

Biological Control

Biological control is the use of the natural enemies of pests (their predators) to control pest population. An example of using biological control is the introduction of the black dot spurge beetle to control the pest weed, leafy spurge.

Biological Control

Another example is using ladybugs to control the population of black aphids (a pest). A single ladybug can consume 6000 aphids in its two to three year lifespan.

Biological Control

Dragonflies are sometimes called “mosquito hawks”. They help control populations of pest insects.

Biological Control

Here, a praying mantis is eating a grasshopper.

Biological Control

There are risks when introducing non-native species for biological control; there may be some concerns about where they will fit into the food chain (Prey, predators, or competitors for the native species?).

Introduced Species

Introduced species are exotic species (non-native) introduced to a new ecosystem. They can be dangerous to an ecosystem because they do not have their natural predators to control their population.

Zebra mussel were accidently introduced to the Great Lakes and now they are a serious problem.

Introduced Species

The European starling was introduced to Central Park in New York City in 1890, and have since taken over many niches from native species as they spread throughout North America.

Introduced Species

The Scotch broom, which is invading BC, started from three seeds on Vancouver Island in 1850. The state of Oregon says that Scotch broom is responsible for $47 million of lost timber each year.

Introduced Species

Purple loosestrife (called the “beautiful killer”) is an invasive species as well. Native to Europe and Asia, it is deadly to other naturally occurring species.

Species in Danger

Many species are in danger of becoming extinct. This is when species no longer exists in the world. A century ago, species became extinct at a rate of one a year. Now, the rate is at least one species per day.

Species in Danger

Some of the ways in which organisms become extinct are:

• Loss of habitat/food shortages/human interactions

• Invasive species• Hunting/poisoning• Pollution• Climate change (e.g. ice age, meteor hitting

earth

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Eastern cougar

Declared extinct March 3, 2011

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Bowhead whale

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Right whale

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Burrowing owl

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Grizzly bear

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Canada:

Sea otter

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Alberta:

Whooping crane

Species in Danger

Organisms that are close to becoming extinct are known as endangered. Here are a few of the endangered organisms in Alberta:

Piping plover