7th Grade Evolution

Marine fossils belonging to the early Cenozoic era are found only in the southern parts of Mississippi. What does this evidence say about the state during this period? (HINT: The lack of fossils could mean that the conditions in the northern parts were different from those in the southern parts.)

• The state was flooded by tropical seas during this period.

• The northern parts of the state were probably above sea level.

• The Mississippi River had a different course during this period.

• The marine animals did not like the weather in the northern parts.

Answer explanation

The lack of marine fossils in the northern parts means that the conditions in the northern parts were different from those in the southern parts of the state. So the northern parts of the state were probably above sea level during the early Cenozoic era.

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Which belongs in the empty box? (HINT: The correct term results in a change in a trait.)

• evolution

• extinction

• fitness

• symbiosis

Answer explanation

Natural selection, the persistence of adaptive traits, leads to evolution, a change in a trait. If a species must change in order to survive, this change results in evolution.

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A change in the genetic make-up, appearance, and behaviors of a species over time is called (HINT: Charles Darwin.)

• evolution.

• adaptation

• natural selection.

• survival of the fittest.

Answer explanation

Evolution. This is the definition for evolution. Natural selection and 'survival of the fittest' describe what makes evolution go forward.

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This lizard looks just like another tree branch. This helps the lizard hide from predators and sneak up on the insects they hunt for food. What do we call the adaptation seen here? (HINT: Like a Hunter!)

• mimicry

• camouflage

• imprinting

• fight or flight

Answer explanation

The lizard blends in with its background. This adaptation is called camouflage.

Consider the model for natural selection. In a population of living things, genetic variation exists. One source of variation is mutation. Which scenario listed here could be a mutation that causes members of a population to die out? (HINT: What is a negative trait?)

• In a population of fast-running cheetahs, some are born that run slower than most.

• In a population of sunflowers, mutations cause some flower heads to produce more seeds.

• In a population of brownish rabbits that live in the tundra, some are born with fur that turns white in the winter.

• In a populations of birds, mutations result in different beak sizes so the birds do not compete for food in the area.

Answer explanation

In a population of fast-running cheetahs, some are born that run slower than most. The slower running cheetahs cannot catch prey. No prey means no food and that limits the chances for survival and reproduction. Slow running may not be passed down to many offspring.

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Over time, organisms change. Sometimes they change so much that descendants may be completely different from their ancestors. What must happen for this process to occur? (HINT: Evolution is change over time.)

• mutations in egg and/or sperm

• no chance for mutations in sex cells

• organisms die before they have a chance to reproduce

• traits acquired during an organism's lifetime is passed on to offspring

Answer explanation

mutations in egg and/or sperm --Through mutation, some offspring are born slightly different than their parents, and through natural selection, if the mutation proves to be an advantage in the current environment, then the organism will survive and reproduce passing the mutation along to future offspring. Over time, species change through random genetic mutations which lead to adaptations by means of natural selection.

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According to Charles Darwin’s theory of natural selection, (HINT: Nature does not deliberately affect the ability of a species to survive.)

• people control evolution.

• the fastest species always survive.

• the strongest species always survive.

• the fittest species survive.

Answer explanation

Natural selection states that the fittest species survive. Thefittest species are able to reproduce more than those that are not well-adapted, and this causes a change in the make-up of populations favoring the well-adapted species.

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Deserts (especially true deserts) are not easy places for animals to live. Animals who live in them often have special features that help them survive. Which adaptation would be helpful for this group of animals? (HINT: The animals must be able to endure the weather.)

• keen eye sight

• short, narrow legs

• tolerate heat

• webbed feet

Answer explanation

tolerate heat

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The early ancestors of the horse (shown in the picture) were adapted to life in tropical forests. Gradually the forests disappeared and were replaced with open grasslands. Because of the gradual change in habitat, modern horses (HINT: The horses lost the protection of the forest trees.)

• have five toes that allow them to walk well on soft ground.

• are herbivores instead of carnivores like their early ancestors.

• are taller with long legs and are capable of great speed to escape predators.

• have gradually grown larger, but show no major changes from the early ancestors.

Answer explanation

Because of the gradual change in habitat, modern horses are taller with long legs and are capable of great speed to escape predators. No longer living in forests, early horses lived in the open grassland and in clear sight of predators. Over time the fastest horses survived and reproduced. Modern horses have also developed teeth that allow them to graze grass instead of browsing in the forest on leaves and insects.

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In order to support his theory of evolutionary change, Charles Darwin concentrated his studies on the many species of finches in the Galapagos Islands. Darwin noted that many of the birds had different shapes and styles of beak.

What is a possible explanation for what Darwin observed? (HINT: Think about why wolves have pointed teeth and cows have flat wide teeth.)

• The birds had beaks that were adapted for feeding differently.

• Some birds had been injured by predators and were poor competitors.

• People had bred the bird to have beaks with varied shapes and sizes.

• The birds always had different beaks.

Answer explanation

Darwin made several collections, drawings and studies of the many species of Galapagos Island finches. Darwin observed that the birds had very different diets, probably to avoid competing for food resources.

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