Threatened, Endangered and
Extinct Species
Standard 4.7
How many species are on
Earth?
Scientists identified about 1.75 million
Could be as many as 100 million
Species can appear and disappear
Extinction
An extinct species is one that no longer
exists.
Extinction is a natural process.
The rate of extinction is increasing due to
human activities such as pollution.
Removing organisms will change
ecosystems.
Effects of Extinction
Causes a loss of animals that help cycle
nutrients through the environment
Lose plants that provide food and oxygen
Loss of organisms that could supply new
medications
Biodiversity
Biodiversity – refers to the great variety of
organisms on Earth
Three major levels
– Genetic
– Species
– Ecosystem
Biodiversity
 Also involves genetic
variation within a
particular species
 Human Examples
– Physical Traits – hair
color, height, eye color
and susceptibility to
disease
Pennsylvania’s Biodiversity
More than 20,000 different species in PA
Besides animals other common organisms
in PA include:
– Insects, plants, fungi and lichens
Scientists in PA are trying to maintain
biodiversity by listing and monitoring as
many species as possible.
Lichens
Pennsylvania’s Biodiversity
4%
7%
23%
3%
Plants/Algae
Insects
16%
Fungi/Lichens
Vertebrates
Protists
Non-insect invertebrates
47%
Interactions Among Organisms
 Remember the food web – all organisms rely on
other organisms
 Predator-prey relationships help to keep an
ecosystem in balance
– An organism of one species (the predator) eats a living
organism of a different species (the prey)
 Examples: polar bears eat fish, lions that eat
zebras, robins that eat worms.
Examples Predator-Prey
Interactions Among Organisms
As the prey population increases,
ecosystems can support more predators
As the prey population decreases, the lack
of prey causes the predator population to
decrease
This allows for a stable carrying capacity
This also allows the strongest and fittest
members of the community to survive
Other relationships
 Symbiosis –
organisms live closely
together over a long
period of time
 Can be parasitic,
mutualistic, or
commensalistic
Other relationships
Parasitism – one species, the parasite, feeds
on a second organism the host
Parasite harms the host by living in or on it
Examples: ticks or mosquitoes that live off
of the host
Parasitism promotes ecosystem stability by
preventing the populations of some
organisms from becoming too large
Parasitism Example
Other relationships
Mutualism – both species involved in the
symbiotic relationship benefit
Examples:
– Bees and flowers – bees feed on flower nectar,
and spread flower pollen in the process
– Lichens – are two organisms, alga and fungus
that grew together
• The algae undergo photosynthesis and provide
food for the fungi and itself while the fungi gathers
water and minerals to share with the algae
Mutualism Example
Other relationships
Commensalism – one organism benefits
while the other is not affected
Example: Trees in the rain forest block
sunlight from reaching the ground,
therefore plants such as orchids establish
roots high in tree branches, growing
through the high canopy to reach sunlight
– The orchid can receive moisture and nutrients
from the air and does not harm the tree
The Human Impact
When humans destroy habitats, kill off
species or pollute the natural environment
biodiversity often decreases
As a result ecosystems break down
Adaptations
Adaptation – special modification or
characteristic that helps an organism better
survive in its environment, and which
typically develops over time or may be
passed down from one generation to
another
Adaptations can be structural (or physical),
behavioral (or responsive)
Structural or Physical
Adaptations
 Examples: desert
plants with thick,
wax-coated leaves
 Predator birds – bald
eagles have keen
eyesight and are
capable of flying at
great speeds in order
to catch prey
Behavioral or Response
Adaptations
 Example: An animal
that cannot regulate
its internal
temperature, such as
lizards or snakes, sit
in the sun on cool
days to warm itself
– Retreats to its burrow
on hot days to cool
itself
Structural Adaptations
 Structural adaptations - are physical
characteristics that help an organism survive in
its environment
 They help animals to perform basic tasks, such as
moving or eating
 Examples – Meat-eating animals have sharp
incisors for killing prey
 Plant eating animals have large, flat teeth that
allow them to grind plants into pieces that are
easily swallowed
Structural Adaptation Examples
Animals in deserts thousands of miles apart
have the same types of adaptations
Plants that grow in the deep shade of
forests have dark green leaves that
increase their ability to catch any light that
reaches the forest floor
Chameleon is a lizard that changes its color
to match its surroundings at the time
Chameleon
Butterflies
 Mimicry – an adaptation
in which one species
copies the appearance or
behavior of another
species
 Recall the “Animal
Camouflage” Article
– Viceroy butterfly protects
itself by looking like the
monarch butterfly, which
birds avoid because of their
bad taste
Adaptation Advantages
 Decreases
competition
 Allows species niche
to be different
 Allows species
survival
Behavioral Adaptations
 The way an organism
acts or responds to its
environment in order
to survive
 Can be reflexive or
instinctive
Reflexive Behaviors
A behavior that is triggered automatically
by something outside an organism
The behavior happens without the
organism thinking about it
– Example: Pulling your hand off of something
hot
– Example: Running from a loud noise
Instinctive Behaviors
A behavior that an organism carries out
because it is genetically prone to do so
These are natural reactions
– Examples: Traveling in a group (safety in
numbers)
– To look bigger and more frightening a
blowfish expands its body with air
– Male bioluminescent fireflies flash light to
attract females
Other Adaptations
Hibernation – animals decrease their
activity during winter months after
constant eating during the fall
Estivation – to avoid the heat of summer
some frogs, lizards and ground squirrels
sleep through the summer in a dormant
state
Other Adaptations
Migration – allows animals to find more
favorable climates or feeding conditions
after a change in climate
Courtship Rituals
 Instinctive behaviors
because they encourage
animal reproduction
– Male birds use songs to
attract female birds
 Structural adaptations
– Male peacock struts using
his colorful tail feathers so
females will notice him
Survival of the Fittest
Which will survive in the snowy climate of
northern Alaska?
– White rabbit with long thick fur or
– Gray rabbit with short fur
Natural Selection
Most helpful traits are passed on to future
generations – Charles Darwin
Process that makes it more likely that
organisms with the best characteristics for
survival in a specific environment will
survive, reproduce, and pass on their
advantageous genetic traits to offspring
Populations
 In order to evolve so the most advantageous
adaptations become common three things must
happen
1. Trait must vary within the species
2. The adaptation must be one that parents can pass on
to offspring genetically
3. One version of the adaptation must benefit the
members to that they survive and reproduce more
than the members who do not have it
 May occur quickly or take millions of years
Amazing Adaptations
 Ice fish
– Evolved to have no
red blood cells and
no hemoglobin
– Oxygen dissolves in
the blood
– Allows fish to
survive in the
extreme cold
Human Impact
 Negative
– Destroying habitat
– Polluting rivers, lakes
 Positive
– Repair damage already
done
– Protect whole
ecosystems (conserve
plants and animals)
– Maintain biodiversity
– Wildlife refuges
– Protect endangered
species
Protecting Endangered Species
 Government protected
habitats
 Bred in captivity and
then returned to wild
– Examples: bald eagle,
California condor
 Restrictions to
hunting
Bald Eagle
In 1700s population of 100,000 in 1970
population of less than 3,000
Cause – unregulated hunting and habitat
destruction, DDT pesticide
DDT – caused eagles to produce eggs with
shells that were too thin
Solution – Government protected eagle’s
nest, bred in zoos, banned use of DDT
Population increased but still endangered
Bald Eagle
PABS
Pennsylvania Biological Survey (PABS)
– Helps to maintain state’s biodiversity
– Tracks and monitors plants and animals
– Coordinates programs, surveys and research
on PA wildlife
– Developing bio-reserves throughout PA
• Help conserve ecosystems throughout the state
Endangered Species Act
ESA – US law that governs the protection
of species whose populations are in decline
and could be in danger of extinction
The law forbids hunting, killing, collecting
or harming of species listed as endangered
or threatened.
3 categories
– Threatened, Endangered, Extinct
ESA Categories
 Threatened
– A species that still has
many individuals in
the wild but whose
numbers are dwindling
to a point at which the
species could become
endangered
– Example: Green snake
 Endangered
– A species that has so
few individuals
remaining that
extinction is a
possibility in the near
future
– Example: Delmarva
fox squirrel
ESA Categories
Extinct
– A species that no longer exists
– Example: Passenger pigeon
Factors Prone to Extinction
 Specific food requirements
 Specific habitat or nesting requirements
 High on food chain or food web
– These animals are more vulnerable to pollution
 Migration
 Reproduce a low rate
 Limited habitat range
 Interference with human activities
Help for Species in Danger
National Marine Fisheries Service and US
Fish and Wildlife Service
– Propose species the ESA will protect
– Can delist species if species is no longer in
need of protection
• Happened to bald eagle in 1999
Humans have accelerated extinction
between 1,000 and 10,000 times