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8th Grade Science
Natural Selection: Critical Juncture Assessment
| Question | Answer |
|---|---|
| Birds with thinner beaks easily reach and eat the seeds inside pinecones. Birds with thicker beaks can easily open and eat seeds with hard shells. If their environment changes to have only seeds in pinecones, which populations will most likely survive? | Only populations that include thin beaked birds would survive because they are they only one who could eat pinecone seeds |
| Foxes that have fur the same color as their environment are better at getting closer to squirrels and catching them to eat. There are now more brown foxes. How did the environment change? | The environment became more brown. |
| After many generations, there were many more brown foxes and fewer white foxes in the population. How did the fox population change? | Brown foxes are more likely to survive, so over generations the white foxes changed to have brown fur. |
| A population of hummingbirds once lived in an environment where there were very few long or medium flowers. The environment changed so that mostly long and medium flowers now grow there. There are now more long beaked hummingbirds. Why? | 2 hummingbirds with short or medium beaks had baby with mutation in its genes for the long-beak trait. That baby survived long enough to pass on its mutation, so the long-beak trait became more common over generations. |
| Guppies have spots on their bodies. Guppy spots that are the same size as the rocks on the bottom make them harder for bigger fish to see and catch. If their environment changes to have only large rocks, which guppy populations will survive? | Only populations with larger spots will most likely survive. |
| Snakes that are the same color as their environment are harder for the eagles to see and catch. After many generations, there were many more red snakes and fewer yellow snakes in the population. How did the environment change? | There was more red dirt in the environment than before. So more red snakes survived and the yellow were eaten by the eagles. |
| How did the snake population change to have fewer yellow snakes? | With each generation, more red snakes survived long enough to pass on the gene for red skin to their offspring so their population numbers increased. |
| Seals with thicker blubber are more likely to stay warm and survive in cold ocean waters, but in warm ocean waters, the seals may overheat and die. What might the seal population look like if the water temperature warmed up? | Only a population with thinner blubber seals could survive due to the warmer water temperatures. |
| What could have caused the seal population to change to thinner blubbered seals in the warmer water? | 2 seals with thick or medium blubber had a baby with a mutation in its genes for the thin trait. Because thin seals are more likely to survive, that baby survived long enough to pass on its mutation, so the thin trait became more common over generations. |
| Cactuses have sharp spines to protect them from being eaten by bighorn sheep. Cactuses with longer spines are less likely to be eaten. If their environment changes to have many bighorn sheep, which of the cactus populations will most likely survive? | Only populations with long spines will be able to survive since the short spines will be eaten and not survive. |
| Brown anoles lizards with shorter legs are better at climbing trees than lizards with longer legs so they are better at escaping from the floods that sometimes cover their islands. How did the environment change to cause more shorter legged lizards? | There were more floods. |
| How did the brown anoles lizard population change over time to survive? | With each generation, more lizards with short legs survived long enough to pass on the gene for short legs to their offspring. |
| A population of medium and large spotted guppies lives in an environment that has always had large rocks. Could there ever have been guppies with small spots in this population? | Yes, a baby guppy could have been born with genes for the mutant small-spot trait and lived for a little while, but it would have died before it had any offspring. |
| Ducks have feathers of different thicknesses to help the ducks stay warm in cold water, but in warm water, thicker feathers can make the ducks overheat and die. In very cold water, which duck populations will most likely survive? | Only duck populations with thicker feathers are more likely to stay warm and survive in cold water. |
| Blue jays use their beaks to get to the seeds they eat. Blue jays with thinner beaks can easily reach and eat the seeds inside pinecones. Over time there have been more thin beaked blue jays in the forest. How did the forest environment change? | There were more trees that had pinecones with seeds. |
| After many generations, there were many more thin beaked blue jays and fewer thick beaked in the population. How did the population change? | With each generation, more blue jays with thin beaks survived long enough to pass on the gene for thin beaks to their offspring. |
| Foxes hunt squirrels for food. Squirrels that have fur the same color as the trees are harder for the foxes to see and catch. If there are only black trees in the forest could there ever have been squirrels with gray fur in this population? | A squirrel could have been born with a mutation in its genes for the gray trait and lived for a little while, but it would have been more likely to die before it had any offspring. |
Created by:
kbieber2023
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