Crunch Time (week of 14-17 April)

Avery and Anika are studying plant and animal cells in their biology class. They learn that both types of cells are eukaryotic, containing organelles and a nucleus with DNA. However, they also discover that plant and animal cells have differences due to their specialized functions.

What differentiates plant cells from animal cells?

CHOOSE THREE

• Plant cells have ribosomes.

• Plant cells lack centrioles.

• Plants cells have a cell wall.

• Plant cells have chloroplasts.

• Plant cells have a cell membrane.

Answer explanation

Plant cells lack centrioles, have a rigid cell wall for structure, and contain chloroplasts for photosynthesis, distinguishing them from animal cells.

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sc.6.L.14.4

Plant and Animal Organelles

Kai and Zoe are comparing and contrasting two of the biological domains using a Venn diagram. These two domains have several characteristics in common. What characteristic could you NOT add to "C"?

• prokaryote

• cell wall

• unicellular

• peptidoglycan

Answer explanation

Peptidoglycan is a specific component of bacterial cell walls, not found in all prokaryotes. Therefore, it cannot be added to 'C' as a common characteristic, unlike prokaryote, cell wall, and unicellular, which are shared.

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sc.6.l.15.1

Classification

Ava and James are breeding mussels. In mussels, the allele for brown coloring (B) is dominant, and the allele for blue coloring (b) is recessive. For which parental genotypes are 100% of the offspring expected to be blue?

• bb x bb

• Bb x Bb

• BB x BB

• BB x bb

Answer explanation

The only parental genotypes that produce 100% blue offspring (bb) are bb x bb. All offspring will inherit the recessive blue allele (b) from both parents, resulting in a genotype of bb.

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SC.7.L.16.1

DNA, Chromosomes, and Heredity

Elijah and Abigail are studying a local ecosystem. Based on the food web, correctly predict how changes in the number of a certain species affect the balance of the ecosystem. Choose each correct statement by clicking on the sentence.

• If the number of rabbits increased, the number of grasshoppers increases.

• If the number of snakes increased, the number of rabbits decreases.

• If the number of rabbits increased, the number of insect-eating birds decreases.

• If the number of hawks increased, the number of grasshoppers increases.

• If the number of hawks increased, the amount of grass increases.

Answer explanation

Increasing snakes reduces rabbits due to predation. More rabbits lead to fewer insect-eating birds as they compete for food. More hawks can increase grasshoppers by reducing their predators, balancing the ecosystem.

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sc.7.L.17.2

Relationships Among Organisms

Aiden and Abigail are studying a typical coastal Maine food web. Predict which species would see the greatest decline in energy availability if fishermen removed the majority of the large piscivorous fish population.

• osprey

• sea ducks

• wading birds

• small planktivorous fish

Answer explanation

Removing large piscivorous fish reduces the top predators, leading to an increase in smaller fish populations. Ospreys, which rely on these large fish for food, would experience the greatest decline in energy availability.

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SC.8.L.18.4

Conservation of Mass and Energy

Noah and Olivia are studying genetics in their biology class. They learn that in a population of rabbits, the allele for long ears (L) is dominant, and the allele for short ears (l) is recessive. Which parental genotypes would result in 50% of the offspring having short ears?

• Ll x ll

• ll x ll

• LL x ll

• Ll x Ll

Answer explanation

The cross Ll x ll produces offspring with genotypes Ll (long ears) and ll (short ears) in a 1:1 ratio, resulting in 50% short-eared rabbits. Other combinations do not yield this ratio.

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NGSS.HS-LS3-1

During a biology class, Evelyn and Oliver are discussing cell structures. Which of the following is NOT a characteristic shared by both eukaryotic and prokaryotic cells?

• Cell membrane

• DNA

• Ribosomes

• Nucleus

Answer explanation

The nucleus is a defining feature of eukaryotic cells, while prokaryotic cells lack a nucleus. Both cell types share a cell membrane, DNA, and ribosomes, making 'nucleus' the correct answer as it is not shared.

In a forest ecosystem, if the population of primary consumers decreases significantly, which group is most likely to increase in population?

• Top predators

• Decomposers

• Secondary consumers

• Producers

Answer explanation

If primary consumers decrease, there is less competition for resources among producers. This allows producers, like plants, to thrive and increase in population due to reduced herbivory.

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NGSS.MS-LS2-1

NGSS.MS-LS2-3

NGSS.MS-LS2-4

In a school garden, which of the following organisms is most likely to be a primary consumer?

• Grass

• Hawk

• Snake

• Grasshopper

Answer explanation

The primary consumer in a food chain is an organism that eats producers. Grass is a producer, while hawks and snakes are secondary consumers. Grasshoppers eat grass, making them primary consumers.

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NGSS.MS-LS2-3

During a biology class, Ethan was asked: Which of the following is a characteristic unique to eukaryotic cells?

• Cell membrane

• DNA

• Ribosomes

• Nucleus

Answer explanation

The nucleus is a characteristic unique to eukaryotic cells, as it houses the cell's DNA. Prokaryotic cells lack a nucleus, making this feature distinct to eukaryotes.