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Chapter 7
MJ Tichich
Sec 7.1
•A characteristic, structure, or behavior that helps an organism live is called an adaptation.
•Sharp teeth and claws of a tiger for catching and eating prey
•Chameleon’s long, sticky tongue is an adaptation for catching insects
•The joints of your legs are an adaptation for walking
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•Adaptations help an organism survive in a particular habitat, the area of place where the organism lives.
•Jackrabbits living in the desert have long ears that provide a large surface area for giving off heat
•Dandelion seeds are carried on the wind which allow dandelions to spread over large areas
•Each habitat has a variety of organisms that live there in different ways. This variety of life is called
diversity. (What kinds of diversity are found in our area, what kinds of adaptations are needed?)
•Many adaptations are found in more than one kind of organism. Similar adaptations occur in organisms
for two main reasons.
•Organisms living in similar conditions will need similar adaptations
•Animals living in cold areas tend to have rounded bodies with short limbs and small ears
providing conservation of heat and less exposure to cold environment
•Fig 7.2 pg 141 Most plants that live in very hot, dry areas have similar adaptations of thick, small, hairy
leaves or no leaves at all. Plants lose water through leaves so these adaptations aid desert plants to
conserve water.
•Related organisms may have similar adaptations
•Large groups of organisms have the same general adaptations needed for survival
•All plants have cell wall and almost all plants have chlorophyll to capture energy from the
sun
•Groups of more closely related organisms also have adaptation in common
All birds have wings and beaks to get food
All fishes have gills and fins
Sea turtles have shells similar to pond turtles
•Organisms that are related to each other may have similar structures even though the structures are used
differently (Fig 7.3 pg 141 OH How are structures similar, how used?)
•Living things that share a large number of characteristics and adaptations may be placed in a group called
a species. All the members of a species have some adaptations that distinguish them from other species
•Pandas have a sixth finger for stripping leaves off bamboo stems. This is an adaptation that is not
shared by any other animal, which means pandas are not the same species as black bears, even
though they look similar.
•No two individuals in a species are exactly the same
•You all look different from each other but you are all Homo sapiens.
•German shepherds and French poodles look different but belong to the same species
•Sometimes adaptations are limiting. How do you overcome your limitations- heat, cold, eyesight.
Sec 7.2
•Variations are the differences within a species. Look at the differences among us, yet we still resemble
our parents because of __________ (genetic inheritance).
•Variation is present in almost every species
•Ladybugs may vary in the number of spots
•Pine trees will have different shapes
Chapter 7
MJ Tichich
•Can you name some variations among dogs, cats or other pets?
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•When two members of the same species reproduce; each contributes genetic material to the offspring.
This mixing of genetic material is called sexual reproduction. This unique mixing adds to the variation
found in the species.
•Remember our sex cells, or gametes (egg and sperm) each contribute 23 single chromosomes to
the zygote. The zygote, or fertilized egg, then has the normal 23 pairs of chromosomes. This
mixing of chromosomes, in humans, translates into 8 million different combinations!
•Most species reproduce sexually
•Some organisms do not do sexual reproduction. Single celled organisms, like bacteria, reproduce through
binary fission where the cell makes an exact replica of itself. This type of reproduction is called asexual
reproduction. In asexual reproduction no genetic material is exchanged.
•Some organisms have the capability of doing both sexual and asexual reproduction. Organisms like the
paramecium get together with another paramecium and trade DNA creating variation among paramecium.
• Variation within a species is caused by variations in genetic traits. Genetic traits can change from what?
(mutations). Mutations happen all the time. Some genes with mutations survive and are passed on to
offspring and become part the gene pool for that species.
• Humans also exhibit variation- can you name some? (hair, skin, eye color, height) Even though we
appear very different from each other we also have very many genes in common with humans living
around the world.
Sec 7.3
• At the age of 22, in 1831, a young man named Charles Darwin set off in a sailing ship named the
Beagle. They were going to study the coast of South America and Darwin’s job was that of naturalist. The
trip lasted 5 years and in that time Darwin saw an incredible number of different living things. He spent
years after the voyage studying the variety of patterns found in nature. He finally worked out a theory to
explain his observations; this theory was the theory of evolution.
Darwin, like other scientists of the time, believed that life on earth had always been the same. 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 living things in England.
Even in climates similar to England, the organisms there were more similar to organism found in other
parts of South America than they were to English organisms. This caused Darwin to ponder why the
organisms were so different when the climates were so similar.
Darwin also found many fossils. He wondered why they died out. Many were similar to living organisms
but much bigger. High on a mountain, Darwin found fossils of oceanic organisms and he wondered how
they got there since the ocean was so far away.
Galapagos Islands
The Galapagos are a chain of 16 islands off the west coast of South America, near the equator. Almost all
the organisms he found on the islands were not found anywhere else. Giant tortoises and iguanas were
found on the islands. Darwin also found a great variety of plants and animals that were different from
those on the other islands.
Chapter 7
MJ Tichich
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Darwin collected 13 species of finches on the Galapagos Islands. Each had a different kind of beak (pg
149). Some beaks were large and thick for cracking seeds. Some were more narrow suitable for eating
insects. Still other beaks that made it capable of eating cacti. This variety was a puzzle for Darwin
because most other finches had just one kind of beak.
After Darwin returned to England he worked for over 20 years answering the questions raised from his
observations. Darwin had seen evidence everywhere that the surface of the earth had changed and was
changing still. He concluded that if organisms did not change along with the world they could not survive.
In 1859 he published his ideas in his book The Origin of Species.
He theorized that organisms are the result of historical change and new species gradually developed from
previous ones. These ideas make up Darwin’s ideas of Evolution, which, in biology, is change over time.
Natural Selection
Darwin also theorized how organisms evolved. He called this hypothesis natural selection. Natural
selection is the process by which those organisms best adapted to their environments survive and pass
their traits onto the next generation. Natural selection works on a population of organisms, not an
individual. A population is a group of individuals of the same species living in a particular area.
Darwin based natural selection on four conditions he observed in nature.
Overpopulation 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.
Limited Resources Food, water, space, and other natural resources are limited. Members of a population
must compete for these limited resources. Darwin referred to this as the struggle for existence.
Variation Not all individuals in a population are exactly the same. Their traits vary slightly. These
variations can be passed from parents to offspring.
Advantage of some variations Some variations can determine which individuals will survive the
struggle for existence and reproduce.
When all of these conditions hold true, organisms best adapted to a particular habitat live longer and
produce more offspring like themselves. Organisms that are not well adapted are more likely to die before
they can reproduce. (Pg 151 peppered moth)
New Species
Natural selection also explains how one species evolves from another. This evolutionary process is called
speciation. Speciation begins when a portion of the population of one species becomes isolated, when
they are not able to breed with other members of the population. A newly formed canyon or mountain
range may divide populations. A division in a lake might divide fish populations. Once the population is
isolated, it can change in a different way from other groups. Mutations might occur or a gene might
become more common through the process of natural selection. Over time, this population may look very
different. Their genes may be different enough to make interbreeding impossible with the organisms that
were once part of the same species. The isolated population has become a different species. (Pg 152 fig
7.12)