Transcript Survival of Species

Survival of
Species
By: Cammie Goodman
Survival of Species
•
You already know that every kind of living thing
has adaptations that help it survive. But what if
conditions changed? Then some plants and
animals might not survive.
Some groups of living things may disappear
What is a species?
A species is a group of living things
that can mate with each other to
produce offspring, or young.
 Bald eagles make up a species,
so do lions. So do humans.
 No two living things are exactly
alike, but members of a species
are a lot like each other.
Long ago, the dinosaurs known as
Tyrannosaurus rex made up a
species. But today, Tyrannosaurs are
extinct, or no longer found living on
earth.
 When a species become extinct, all
its members have died out. An
extinct species is gone forever.
 We know about Tyrannosaurs
and other dinosaurs only from
fossils.
 A fossil is the remains or trace
of an organism that lived long
ago.
 People have found fossils of
dinosaur bones and teeth.
 The picture below shows a
Tyrannosaurus rex skeleton.
Scientist constructed it using
fossil bones.
How Species Survive
No species would be alive today if its members
could not reproduce.
 Recall that when living things reproduce, they
make more living things of the same kind.
 Lions produce more lions; bald eagles produce
more bald eagles and so on.
 In animals, the process begins when a male and
female of a species mate. It ends with the birth
or hatching of offspring.
Every animal or plant comes to the
end of its life and dies.
 Species survive because their member reproduces.
 But suppose that animals of a certain kind die faster
than they can produce offspring.
 The number of animals of that kind will get smaller
and smaller, until the species is extinct.
 An endangered species is one that is in danger of
disappearing, or becoming extinct.
 Events in nature can cause a species to become
endangered or extinct. So can human activities.
Events in Nature
Affect Species
Long before people lived on Earth,
species of plants and animals
become extinct. Events in nature
caused them to die faster than they
could reproduce
 Climates changed from warm to cold.
Species that could not live in cold places
did not survive long enough to
reproduce. They became extinct.
 Jungles turned into deserts. Jungle
species that could not survive in hot, dry
deserts became extinct
 In some places, floods covered land that
had been dry. Species that could not live
and reproduce in wet places died out.
 New predators appeared. Animals that could not
defend themselves or hide were eaten faster than
they could reproduce. These animals’ species died
out.
 New species appeared that could compete better for
resources than existing species. Recall that members
of different populations compete, or fight, for the
same resources. When a new competing species got
too much of a resource, an existing species could
become extinct.
Did you know?
• People hunt tigers, cheetahs,
and snow leopards for their
fur.
• Hunting and other human
activities endangered these
animals.
Here are the top 10 most endangered species,
according to World Wildlife Fund:
1. Tiger
2. Polar Bear
3. Pacific Walrus
4. Magellanic Penguin
5. Leatherback Turtle
6. Bluefin Tuna
7. Mountain Gorilla
8. Monarch Butterfly
9. Javan Rhinoceros
10.Giant Panda
Scientists know that many species died out at the
same time, about 65 million years ago.
Scientists think they died because an
object from space crashed on Earth.
 The crash threw huge amounts of dust into the
air. The dust blocked out sunlight.
 Many plants died because they did not have
sunlight to make food.
 Then many animals that ate those plants died.
 So did animals, such as carnivores, that fed on
those plant-eaters.
 Dinosaurs and many species became extinct.
Human Activities Affect
Other Species
Today, events in nature still
cause species to die out. But
human activities are also
putting species in danger.
Hunting can cause a species to
disappear.
 That is what happened to
Carolina parakeets.
 These bright-colored birds
used to live in Georgia and
other southeastern states.
 But farmers killed the bird
because they ate crops.
• Farmers shot so many
Carolina parakeets that by
1920 the species was extinct
People also destroy habitats.
 Recall that a habitat is where a
plant or animals lives.
 Besides hunting Carolina
parakeets, farmers cut down
forests where the birds live.
 Smaller habitats meant that few
birds could survive.
 Today, the loss of their habitats
puts many species in danger.
People put harmful materials into the
environment.
 These materials are called pollutants.
Farmers used to spray their crops with a
chemical called DDT.
• The chemicals killed insects that
fed on the crops.
• Then DDT got into the bodies of
animals that ate the insects.
• When eagles and hawks ate
these animals, the DDT got into
their bodies
 The DDT made the birds produce eggs with very
weak shells.
 Many of the shells broke before young birds
could hatch.
 Some bird species, such as Georgia’s bald eagle,
almost became extinct.
 Since 1972, it has been against the law to use
DDT in the United States.
 Other pollutants have put species in danger,
too.
Discussion Question:
Suppose a species of bird cannot
find safe places to build nests.
What may happen to that
species?