Transcript Diversity of Living Things

Adaptations, Variation, & Natural Selection
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How are the ostrich and hummingbird
different?
◦ Each bird has a beak, wings, and feet, but each
body part is a different size and shape
◦ These structural differences not only look different,
but they are used differently.
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Hummingbird’s wings allow it to hover at a
flower while it sucks nectar with its long,
narrow beak.
Ostrich’s long, powerful legs allow it to run at
fast speeds
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A characteristic, structure, or behavior that
helps an organism live in its environment is
an adaptation.
◦ Adaptations help organisms get food, protect
themselves, move, reproduce, and carry on life
processes.
 Sharp teeth and claws help a tiger catch and eat prey
 Joints of your legs allow people to walk
 Long, sticky tongue allows chameleon to catch insects
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Adaptations help organisms survive in a
particular habitat.
◦ A habitat is the area or place where an organism
lives
◦ With its adaptations, an organism is adapted to its
environment
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Many different habitats exist on the earth
Each habitat has a variety of organisms that
live there in different ways
The variety of life is called diversity
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Coconuts, which are the seeds of
one kind of palm tree, can float
from island to island because of
their thick, airy husks.
Bats can move freely in darkness by
sending out sound waves. When
the sound waves hit an object, they
echo back to the bat’s large ears.
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The powerful front legs and
half-meter-long tongue of the
anteater help it get into the
hard mounds of termites.
Dandelion seeds are carried
on the wind by an umbrellalike structure to spread over
large areas.
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Many adaptations are found in more than one
kind of organism.
Similar adaptations occur in organisms for
two main reasons.
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In order to survive the same kinds of conditions,
organisms need similar adaptations.
◦ Animals living in cold areas tend to have rounded bodies
with short limbs and small ears
 What are some animals that fit that description??
 These body shapes expose the least amount of body surface
to the cold environment and help conserve body heat
◦ Plants that live in very hot, dry areas tend to have thick,
small, hairy leaves, or no leaves at all.
 Since plants lose water through their leaves,
these adaptations help desert plants
conserve water.
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Organisms may have similar adaptations
because they are related to each other.
Large groups of organisms have the same
general adaptations needed for survival
◦ All plants have cell walls and almost all plants have
chlorophyll to capture energy from sunlight.
◦ All birds have wings and use beaks to get food, no
matter where they live
◦ All fishes have gills and fins
◦ Frogs and toads all have strong back
legs for hopping and swimming.
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Living things that share a large number of
characteristics and adaptations may be
placed in a group called a species.
◦ A species is made up of organisms that look similar
and can mate with each other to produce offspring
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All the members of a species have some
adaptations that distinguish them from other
species.
◦ Pandas have a sixth finger, which developed from a
wrist bone, and is used for stripping leaves off
bamboo stems
 This is an adaptation that is not shared by any other
animal
 Pandas are not the same species as bears,
even though they look a lot alike
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No two members of a species are exactly
alike
◦ People all look different from each other but are all
human beings.
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Sometimes it is very difficult to tell whether
two organisms belong to the same or
different species
◦ German shepherds and French poodles look
different, but they belong to the same species
◦ African elephants and Indian elephants look very
similar but are in different species
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You share adaptations with people all over
the world.
◦ All people are endothermic and have a protective
coating of skin.
◦ All people see things in three dimensions and most
people see things in color.
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Sometimes your adaptations are limited, but
you overcome them regularly
Your body temperature remains constant, but
you still get cold
◦ You overcome that by wearing warm clothing and
heating your surroundings
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If you can’t see something from a great
distance, you use a telescope or binoculars
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What is an adaptation? Give two examples of
human adaptations and two other examples.
What adaptations do humans have that make
it possible for them to ride a bike?
Explain how sight, touch, and smell are useful
adaptations for a family of new kittens.
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How are they alike? How are they different?
◦ Even though they have similar ears and body
shapes, their color patterns and sizes are not the
same.
◦ Still, each kitten resembles its parents, which is a
result of inheritance from both parents.
◦ Because each kitten looks a little different, this
family of kittens has a variety of traits.
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The differences among the kittens is an
example of variation within a species
Variation is easy to see among humans
We are all different shapes, sizes, and colors
Differences exist among the individuals of
almost every species
◦ Ladybugs have different number of spots
◦ Pine trees may have different shapes
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Individual variation shows up in physical
traits and in the genetic material
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Sexual reproduction: reproduction through
the union of a male and a female gamete (sex
cells), each contributing genetic material to
the offspring.
◦ Produces new genetic combinations because half
the genes come from the mother and half from the
father
 Genes could be shuffled into at least eight million
different combinations, thus making unique genetic
material which is responsible for the variation within a
species
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Most species reproduce sexually, but not all
living things need a partner to reproduce.
A single-celled organism divides by fission to
form two new individuals
◦ The new cells get their genes form just one parent.
◦ The two cells are exact copies of each other
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When reproduction takes place through the
copying of just one individual’s genetic
material, it is called asexual reproduction.
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Variation within a species occurs because different
individuals have different forms of the same genes.
Sexual reproduction creates new combinations of
genes, but how are different genes created in the first
place?
◦ Genes change when a mutation occurs
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A small number of genes changed by mutation in sex
cells survive and are passed on, becoming part of the
species gene pool.
As a result of mutation and sexual reproduction, the
genes of the individuals in a species show variety.
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Differences
◦ Each human is unique
◦ Legs, arms, ears, and noses are all different sizes
and shapes
◦ Hair, skin, eye color
 Differences in skin color is the result of a greater or
lesser amount of a protein called melanin
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Despite variation, every human being shares
a huge number of the same genes and
proteins with humans living all over the world
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In the fall of 1831, Charles Darwin set out on a voyage to
study and chart the South American coastline on the sailboat
Beagle.
◦ The voyage lasted five years
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Darwin was the ship’s naturalist: person who studies the
world of nature
He saw an incredible number of different living things, but
the variety of patterns in nature puzzled him.
He spent years after his return working out a theory to
account for his observations that eventually caused a
revolution in the study of biology.
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Before leaving England, Darwin studied the
plants and animals
He also studied the ideas of the scientists of
his time
◦ Most scientists believed that the earth and life on it
had always been the same
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During the first part of the voyage, Darwin
explored the tropical forests, the plains, and the
very cold places in South America
He noticed that nearly every living thing there
was very different from the living things in
England
Even in the parts of SA where the climate was
similar to England, the living things were more
similar to other SA organisms.
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Darwin wondered why the organisms in these two
places were so different even though the climates
were similar.
Darwin also found many fossils
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They were the remains of organisms that no longer
existed
Many were similar to living organisms, but usually bigger
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Darwin’s ideas were greatly influenced by the life forms
on the Galapagos Islands
Almost all of the organisms that were found on these
islands were not found anywhere else
They were even different than organisms on any of the
other islands in SA
Darwin collected 13 species of finches on the islands,
each with a different kind of beak
◦ Large, thick beaks for cracking seeds
◦ Narrow beaks for eating insects
◦ A few had beaks that were for eating cacti
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In most places, finches had one type of
beak and if they had different kinds of
beaks, they were different kinds of birds.
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After his return to England, Darwin worked
for over 20 years to figure out what he found
in South America
Darwin had seen evidence that the surface of
the earth had changed and was still changing
He concluded that if the organisms in this
changing world didn’t change along with it,
they could not survive.
In 1859, he published his ideas in a book
called The Origins of Species.
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Darwin claimed that organisms are the
products of historical change and that new
species gradually develop from previous
ones.
He said that all life shares a single and
complex history
These ideas make up Darwin’s theory of
evolution
◦ Evolution: the process by which species change
over time
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Darwin not only said that life forms evolved, he
hypothesized about how they evolved.
Darwin called his hypothesis natural selection
Natural selection: process by which those
organisms best adapted to their environment
survive and pass their traits on to the next
generation.
◦ Works on a population of organisms, not individuals
 Population: group of individuals of the same species
living in a particular area
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Survival of the fittest: another term for
Darwin’s natural selection, or preservation of
favored races in the struggle for life
Darwin based natural selection on four
conditions he observed in nature,
overproduction, limited resources,
variation, and advantage of some variations.
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Living things produce more young than can
survive
Populations tend to stay the same size over a
period of time, despite the large number of
young produced
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Food, water, space, and other resources are
limited
Members of a population must compete for
these limited resources
Darwin called this the struggle for existence
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Not all individuals in the population are
exactly the same
Their traits vary slightly
These variations can be passed from parents
to offspring
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Some variations can determine which
individuals will survive the struggle for
existence and reproduce
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Organisms best adapted to a particular
habitat live longer and produce more
offspring like themselves
Organisms not well adapted die before they
can reproduce
Over generations, the number of welladapted individuals increases
◦ The traits and characteristics of the population as a
whole change.
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Because of natural selection, a population
always tends to be adapted to its habitat
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Life did not exist on the earth until about 3.5
billion years ago.
◦ The organisms alive at that time were simple cells
without nuclei
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Earth was very different than what it is now.
◦ Atmosphere was made up of gases that would be
poisonous to most of today’s living organisms
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Continents shifted and moved apart
Mountain ranges formed
Sheets of ice covered parts of the earth, then
retreated
All of these changes have affected living
things and the way they evolved
Also, living things changed the earth
◦ Photosynthesis made the atmosphere fill with
oxygen
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Scientists use a timeline to show the 4.6
billion year history of the earth and its life
◦ Called a scale of geologic time
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The largest kind of time division is called an
era, which is measured in millions of years
Four eras, but they are not equal lengths
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Precambrian Era
Paleozoic Era
Mesozoic Era
Cenozoic Era
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3.5 billion years ago
Longest lasting era (more than all 3 other
eras combined)
Started with single cell organisms without
nuclei
After millions of years, fungi & algae evolved
Near the end of the era, oceans began to fill
with many-celled sponges, jellyfish, and
worms
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570 million years ago
Many new life forms gradually appeared
Trilobites and other animals without
backbones became common in the oceans
Then fishes evolved
About halfway through this era, reptiles,
insects, and amphibians started to appear
By the end of the era, most animal species
living in the oceans died out
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245 million years ago
Dinosaurs of all sizes were the most common
form of animal for most of this era
Mammals evolved early in the era
Birds evolved midway through the era
Also, about midway through this era is when
Pangea broke up into separate continents
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65 million years ago
Mammals became very numerous and evolved
into many different species
Horses and camels appeared about 40 million
years ago
Large grazing animals and whales evolved
after that
Sheets of ice covered the earth, then receded
Towards the end of this era, the first
humans appeared.
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When landforms are worn down by wind and
water, pieces of rocks called sediments are
created
Sediments pile up, layer by layer
They get squeezed together to form layers of
rocks, called sedimentary rocks
◦ They provide clues to how the earth changed over
time
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Layers of rocks closest to the surface formed
after the layers below them
Lower layers are older than the upper layers
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In radioactive dating, the amounts of two
elements in the rock are measured
◦ One is a radioactive element which changes into
another element at a constant rate
◦ The other is the element the first one changes into
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When the amounts of the two elements are
compared, a rock’s age can be determined
In the oldest rocks, most of the radioactive
element has changed into the other element
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List the four eras of geologic time in order.
Identify the era in which each of the following
first appeared: humans, fishes, birds, worms,
reptiles.
What were some important adaptations for
animals living during the Cenozoic Era?
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Scientists use the records left by organisms
that once lived to learn about past life on the
earth
Part of life’s records
◦ Bones, teeth, shells,
◦ Prints from leaves, animal footprints
◦ Outlines from body parts left in rocks
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The preserved remains and traces of
organisms that lived in the past are called
fossils.
◦ Show differences between organisms today and
those of the past
◦ Provide evidence that earlier forms of life have died
out or become extinct
◦ Fossils provide a record of life called the fossil
record
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Most fossils are found in rocks that formed
from layers of sand, mud, or silt
◦ Show the outlines of the hard parts of the
organism, such as its shell or bones
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Organisms that left these fossils were covered
by sediments after they died
◦ The soft parts of the organism decayed
◦ After a long period of time, the sediment covering
the skeleton became a layer of rock
◦ Water seeps through the rock and dissolved the
bones or shells, leaving an impression called a mold
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For many fossils, one last step occurred
Minerals carried by the water built up in the
mold to form a cast
There are other types of fossils that form by
organisms being trapped in the sap from
trees or frozen in ice called a body fossil.
◦ These organisms get preserved and the soft parts
don’t decay
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By piecing together the clues provided by the
fossil record, scientists have constructed a
tree shaped diagram that shows evolutionary
relationships among the different groups of
organisms
The base of the tree represents the earliest
forms of life that all other organisms evolved
from
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Many animals look similar during their early
stages of development
◦ Species with similar embryos probably have a
common ancestor
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Similarities in the DNA of different organisms
also show how closely organisms are related
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Fossils can provide clues to how different life
forms are related to each other
◦ Fossils of fishes with leg-like fins are found in
layers above fossils or fishes
◦ Above both layers, there are fossils of animals that
have legs (they look like they lived in water part of
the time)
◦ Above that layer are reptiles
◦ What would you conclude from this evidence???
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Humans belong in a group of mammals called
the primates
◦ Appeared more than 65 million years ago as
animals adapted to living in trees
 Requires special adaptations
 Hands must grasp branches
 Arms must have a wide range of motion for swinging
 Eyes must judge distance accurately for rapid movement
(facing forward so the fields of vision overlap)
 Humans have similar traits
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After the first primates appeared, they
evolved in different directions
◦ Some continued to live in drives and evolved into
many species of lemurs, monkeys, and other similar
primates of today
◦ Others adapted to living at least part of the time on
the ground and evolved into many species of
modern apes, chimpanzees, gorillas, and
orangutans
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Between 4 and 8 million years ago, some
apelike primates began to adapt to living
entirely on the ground
The evolved to have a skeleton for standing
and walking upright on two legs
These primates were ancestors of modern
humans called hominids, or humanlike
primates (Lucy, found in 1974 in Africa)
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Many other fossils of extinct hominids have
been found
Around 2.5 million years ago, a species of
hominid developed a larger brain and began
to use tools
◦ This hominid was the first member of the genus
Homo, which includes modern humans
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The most widely known early hominids that
are classified as Homo sapiens are the
Neanderthals
◦ Lived between 230,000 and 30,000 years ago
◦ Looked much different from modern humans even
though they belong to the same species
 Neanderthals were short with large bones and heavy
brows
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Intelligent hunters who used tools and fire
and made clothes from animal hides
Lived in cooperative social groups and cared
for the aged and sick
Used language and could pass on knowledge
and traditions from generation to generation
Neanderthals disappeared about 30,000
years ago
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First group of modern humans were the CroMagnons
Appeared about 100,000 years ago, possibly
in Africa
Some scientists think they caused the
extinction of the Neanderthals
Cro-Magnons looked very similar to modern
humans
◦ Smaller teeth, longer faces, straighter foreheads
than Neanderthals
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Used language and created music and art
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How does a mold form?
What kinds of evidence do fossils provide
about life’s history?
What characteristics do humans share with
apes, such as chimpanzees?
In what ways are modern humans different
from the first hominids?