Download Lesson 5 - Human Activity and Ecosystems - Hitchcock

Unit 2 Lesson 5 Human Activity and Ecosystems
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
Growing Pains
How do humans negatively affect
ecosystems?
• An ecosystem is all of the living and nonliving
things within a given area.
• Changing one thing in an ecosystem can affect
many other things, because everything in an
ecosystem is connected.
• Humans can affect ecosystems through pollution.
Pollution is caused by any material or condition
that harms the environment.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans negatively affect
ecosystems?
• The growing human population has created a
greater need for natural resources, leading to
changes in ecosystems.
• The overuse of resources causes them to be
depleted, or used up.
• Resource depletion occurs when a large fraction of
a resource has been used up.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans negatively affect
ecosystems?
• Compare the time it took for the human
population to grow from 1 billion to 2 billion, and
from 3 billion to 6 billion.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans negatively affect
ecosystems?
• Human population growth in and around cities is
called urbanization.
• Urban growth within ecosystems often destroys
natural habitats and can bring humans and wildlife
into contact.
• Every habitat has its own number and variety of
organisms, or biodiversity. If a habitat is
damaged or destroyed, biodiversity is lost.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
Water, Water Everywhere
How do humans impact oceans?
• Oceans support various ecosystems that together
contain nearly half of Earth’s species. Pollution
damages these ecosystems and threatens
biodiversity.
• Point-source pollution comes from one source,
such as an oil spill.
• Nonpoint-source pollution comes from many
sources, such as when chemical fertilizers and
pesticides are washed into oceans.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans impact oceans?
• A greater demand for seafood from the growing
human population has led to overfishing of some
ocean species.
• If a fish population cannot reproduce fast enough,
it may become locally extinct.
• The local loss of a species can disturb ocean food
webs and threaten ecosystem stability.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans impact oceans?
• The growing human population has led to
increased coastal development and has increased
pollution on shore and in coastal waters.
• In some places, development has almost
completely replaced natural coastlines, destroying
mangrove forests that protect coastlines.
• Human activity has also damaged coral reefs, but
scientists and others are working to correct this
damage.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans affect freshwater
ecosystems?
• In many river ecosystems, human activities have
decreased the amount of water, or water quantity.
• Dams block the flow of river water, leading to less
water downstream.
• If the natural course of a river is changed by
channelization, it changes the water quantity,
temperature, and chemistry. This affects river
species.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans affect freshwater
ecosystems?
• Human activities can also decrease water quality,
or how good the water is. Fertilizers contain
nutrients that can enter ponds and lakes as runoff.
• An increase in the amount of nutrients, such as
nitrates, in an aquatic ecosystem is called
eutrophication.
• Excess nutrients in ponds and lakes cause
overgrowth of algae, using up the pond’s
dissolved oxygen and causing fish to die.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans affect freshwater
ecosystems?
• Water quality is also affected by air pollution.
• Burning fossil fuels releases chemicals into the air,
and some of the chemicals combine with rain to
produce acid rain.
• Acid rain can damage both aquatic and land
ecosystems.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
Exotic Species
• An organism that makes a home for itself in a new
place outside its native home is an exotic species.
• Exotic species that outcompete native species are
called invasive exotic species.
• When European rabbits were introduced into
Australia, their population exploded because they
had plenty of space and food, but no predators.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
Save It!
How do humans protect ecosystems?
• The careful and responsible management of a
resource is called stewardship.
• The organisms in an ecosystem depend on each
other and interact to form a vast food web. The
loss of a species can leave gaps in the web.
• Humans can protect habitats and help species
survive, thereby protecting the biodiversity and
health of an ecosystem.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 5 Human Activity and Ecosystems
How do humans protect ecosystems?
• Conservation is the protection and wise use of
natural resources.
• Practicing conservation means using fewer natural
resources and reducing waste. It also helps
prevent habitat destruction.
• There are “three Rs” for conserving resources:
reduce what you buy and use; reuse what you
already have; and recycle by recovering materials
from waste.
Copyright © Houghton Mifflin Harcourt Publishing Company