id: 17723
lecture: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The strength of a force is called its magnitude. The greater the magnitude of the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the magnitude of a magnetic force between two magnets by using magnets of different sizes. The magnitude of the magnetic force is greater when the magnets are larger.
question: Think about the magnetic force between the magnets in each pair. Which of the following statements is true?
choice: (A) The magnitude of the magnetic force is the same in both pairs. (B) The magnitude of the magnetic force is greater in Pair 2. (C) The magnitude of the magnetic force is greater in Pair 1.
context: The images below show two pairs of magnets. The magnets in different pairs do not affect each other. All the magnets shown are made of the same material, but some of them are different sizes.
answer: C
rationale: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The strength of a force is called its magnitude. The greater the magnitude of the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the magnitude of a magnetic force between two magnets by using magnets of different sizes. The magnitude of the magnetic force is greater when the magnets are larger. Magnet sizes affect the magnitude of the magnetic force. Imagine magnets that are the same shape and made of the same material. The larger the magnets, the greater the magnitude of the magnetic force between them. Magnet A is the same size in both pairs. But Magnet B is larger in Pair 2 than in Pair 1. So, the magnitude of the magnetic force is greater in Pair 2 than in Pair 1. The answer is B.
generated_skill:
solution: The magnets in Pair 2 attract. The magnets in Pair 1 repel. But whether the magnets attract or repel affects only the direction of the magnetic force. It does not affect the magnitude of the magnetic force. Magnet sizes affect the magnitude of the magnetic force. Imagine magnets that are the same shape and made of the same material. The larger the magnets, the greater the magnitude of the magnetic force between them. Magnet A is the same size in both pairs. But Magnet B is larger in Pair 1 than in Pair 2. So, the magnitude of the magnetic force is greater in Pair 1 than in Pair 2.
skill: Compare magnitudes of magnetic forces
id: 17819
lecture: Gymnosperms are plants that have seeds but not flowers. Conifers are a type of a gymnosperm. Instead of flowers, conifers have cones. Conifers use their cones for sexual reproduction. Most conifer trees have both male and female cones. The male cones produce pollen. The female cones produce eggs and a sticky substance on the edge of the cone. Male cones release pollen into the wind. Pollination happens when pollen lands on and sticks to the female cones. Self-pollination happens when pollen sticks to a female cone on the same tree. Cross-pollination happens when pollen sticks to a female cone on a different tree. After pollination, sperm from the pollen fuse with eggs at the base of the female cone's scales. This is called fertilization. The fertilized eggs grow into seeds inside the female cone. Conifer seeds are released from the fertilized cones. Many conifer seeds have wing-like structures. They can be carried long distances by the wind. When a seed lands on the ground, it can germinate and grow into a new plant. The new plant can grow cones and begin the conifer life cycle again.
question: What grows in a fertilized cone?
choice: (A) pollen (B) seeds
context: This diagram shows the life cycle of a pine tree.
answer: B
rationale: Gymnosperms are plants that have seeds but not flowers. Conifers are a type of a gymnosperm. Instead of flowers, conifers have cones. Conifers use their cones for sexual reproduction. Most conifer trees have both male and female cones. The male cones produce pollen. The female cones produce eggs and a sticky substance on the edge of the cone. Male cones release pollen into the wind. Pollination happens when pollen lands on and sticks to the female cones. Self-pollination happens when pollen sticks to a female cone on the same tree. Cross-pollination happens when pollen sticks to a female cone on a different tree. After pollination, sperm from the pollen fuse with eggs at the base of the female cone's scales. This is called fertilization. The fertilized eggs grow into seeds inside the female cone. Conifer seeds are released from the fertilized cones. Many conifer seeds have wing-like structures. They can be carried long distances by the wind. When a seed lands on the ground, it can germinate and grow into a new plant. The new plant can grow cones and begin the conifer life cycle again. Growth and reproduction can happen at the same time. So, the conifer can use its energy to grow and reproduce. A pine tree's cones can be male or female. A female pine tree's cones have a sticky substance on the edge. A male pine tree's cones release pollen. So, pollen grows in a fertilized cone. The answer is A.
generated_skill:
solution: Fertilized eggs grow into seeds inside a fertilized cone. Pollen grows inside male cones, not fertilized cones.
skill: Angiosperm and conifer life cycles
id: 18662
lecture:
question: Which of these cities is marked on the map?
choice: (A) New York City (B) Washington, D.C. (C) Philadelphia (D) Boston
context: N/A
answer: C
rationale: The city is Washington, D.C. Philadelphia, New York City, and Boston are marked with gray circles on the map below. The answer is B.
generated_skill:
solution: The city is Philadelphia, Pennsylvania. New York City, Boston, and Washington, D.C., are marked with gray circles on the map below.
skill: Cities of the Northeast
id: 19112
lecture: A material is a type of matter. Wood, glass, metal, and plastic are common materials. Some objects are made of just one material. Most nails are made of metal. Other objects are made of more than one material. This hammer is made of metal and wood.
question: Which material is this clothes hanger made of?
choice: (A) cardboard (B) wood
context: N/A
answer: B
rationale: A material is a type of matter. Wood, glass, metal, and plastic are common materials. Some objects are made of just one material. Most nails are made of metal. Other objects are made of more than one material. This hammer is made of metal and wood. Look at the picture of the clothes hanger. The clothes hanger is made of two different materials. The top part is made of cardboard. The rest of the hanger is made of metal. Cardboard is a strong material. It is made of wood pulp. The answer is A.
generated_skill:
solution: Look at the picture of the clothes hanger. The clothes hanger is made of two different materials. The hook is made of metal. The rest of the hanger is made of wood.
skill: Identify multiple materials in objects
id: 19227
lecture: Offspring phenotypes: dominant or recessive? How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype. If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait. If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait. A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type. For example, consider the Punnett square below. | F | f F | FF | Ff f | Ff | ff There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2.
question: What is the expected ratio of offspring with white spots to offspring with solid coloring? Choose the most likely ratio.
choice: (A) 4:0 (B) 3:1 (C) 1:3 (D) 2:2 (E) 0:4
context: In a group of cows, some individuals have solid coloring and others have white spots. In this group, the gene for the coat pattern trait has two alleles. The allele for white spots (a) is recessive to the allele for solid coloring (A). This Punnett square shows a cross between two cows.
answer: E
rationale: Offspring phenotypes: dominant or recessive? How do you determine an organism's phenotype for a trait? Look at the combination of alleles in the organism's genotype for the gene that affects that trait. Some alleles have types called dominant and recessive. These two types can cause different versions of the trait to appear as the organism's phenotype. If an organism's genotype has at least one dominant allele for a gene, the organism's phenotype will be the dominant allele's version of the gene's trait. If an organism's genotype has only recessive alleles for a gene, the organism's phenotype will be the recessive allele's version of the gene's trait. A Punnett square shows what types of offspring a cross can produce. The expected ratio of offspring types compares how often the cross produces each type of offspring, on average. To write this ratio, count the number of boxes in the Punnett square representing each type. For example, consider the Punnett square below. | F | f F | FF | Ff f | Ff | ff There is 1 box with the genotype FF and 2 boxes with the genotype Ff. So, the expected ratio of offspring with the genotype FF to those with Ff is 1:2. To determine how many boxes in the Punnett square represent offspring with white spots or solid coloring, consider whether each phenotype is the dominant or recessive allele's version of the coat pattern trait. The question tells you that the a allele, which is for white spots, is recessive to the A allele, which is for solid coloring. White spots is the recessive allele's version of the coat pattern trait. A cow with the recessive version of the coat pattern trait must have only recessive alleles for the coat pattern gene. So, offspring with white spots must have the genotype aa. All 4 boxes in the Punnett square have the genotype aa. Solid coloring is the dominant allele's version of the coat pattern trait. A cow with the dominant version of the coat pattern trait must have at least one dominant allele for the coat pattern gene. So, offspring with solid coloring must have the genotype AA or Aa. There are 0 boxes in the Punnett square with the genotype AA or Aa. So, the expected ratio of offspring with white spots to offspring with solid coloring is 4:0. This means that, based on the Punnett square, this cross will always produce offspring with white spots. This cross is expected to never produce offspring with solid coloring. The answer is A.
generated_skill:
solution: To determine how many boxes in the Punnett square represent offspring with white spots or solid coloring, consider whether each phenotype is the dominant or recessive allele's version of the coat pattern trait. The question tells you that the a allele, which is for white spots, is recessive to the A allele, which is for solid coloring. White spots is the recessive allele's version of the coat pattern trait. A cow with the recessive version of the coat pattern trait must have only recessive alleles for the coat pattern gene. So, offspring with white spots must have the genotype aa. There are 0 boxes in the Punnett square with the genotype aa. Solid coloring is the dominant allele's version of the coat pattern trait. A cow with the dominant version of the coat pattern trait must have at least one dominant allele for the coat pattern gene. So, offspring with solid coloring must have the genotype AA or Aa. All 4 boxes in the Punnett square have the genotype AA or Aa. So, the expected ratio of offspring with white spots to offspring with solid coloring is 0:4. This means that, based on the Punnett square, this cross will never produce offspring with white spots. Instead, this cross is expected to always produce offspring with solid coloring.
skill: Use Punnett squares to calculate ratios of offspring types
id: 19397
lecture: An adaptation is an inherited trait that helps an organism survive or reproduce. Adaptations can include both body parts and behaviors. The color, texture, and covering of an animal's skin are examples of adaptations. Animals' skins can be adapted in different ways. For example, skin with thick fur might help an animal stay warm. Skin with sharp spines might help an animal defend itself against predators.
question: Which animal is also adapted to be camouflaged in a sandy desert?
choice: (A) horned viper (B) European green lizard
context: s live in the deserts of southern Africa. The is adapted to be camouflaged in a sandy desert. Figure: Namaqua chameleon.
answer: A
rationale: An adaptation is an inherited trait that helps an organism survive or reproduce. Adaptations can include both body parts and behaviors. The color, texture, and covering of an animal's skin are examples of adaptations. Animals' skins can be adapted in different ways. For example, skin with thick fur might help an animal stay warm. Skin with sharp spines might help an animal defend itself against predators. Look at the picture of the Namaqua chameleon. The Namaqua chameleon has sand-colored scales covering its body. It is adapted to be camouflaged in a sandy desert. The word camouflage means to blend in. Now look at each animal. Figure out which animal has a similar adaptation. The European green lizard has green, brown, and yellow scales covering its body. It is adapted to be camouflaged in a sandy desert. The horned viper has a sand-colored body. It is adapted to be camouflaged in a sandy desert. The answer is B.
generated_skill:
solution: Look at the picture of the Namaqua chameleon. The Namaqua chameleon has sand-colored scales covering its body. It is adapted to be camouflaged in a sandy desert. The word camouflage means to blend in. Now look at each animal. Figure out which animal has a similar adaptation. The horned viper has sand-colored scales covering its body. It is adapted to be camouflaged in a sandy desert. The European green lizard has a green, brown, and yellow body. It is not adapted to be camouflaged in a sandy desert.
skill: Animal adaptations: skins and body coverings
id: 19782
lecture: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is weaker when the magnets are farther apart.
question: Think about the magnetic force between the magnets in each pair. Which of the following statements is true?
choice: (A) The magnetic force is weaker in Pair 1. (B) The strength of the magnetic force is the same in both pairs. (C) The magnetic force is weaker in Pair 2.
context: The images below show two pairs of magnets. The magnets in different pairs do not affect each other. All the magnets shown are made of the same material.
answer: C
rationale: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is weaker when the magnets are farther apart. Distance affects the strength of the magnetic force. When magnets are farther apart, the magnetic force between them is weaker. The magnets in Pair 1 are farther apart than the magnets in Pair 2. So, the magnetic force is weaker in Pair 1 than in Pair 2. The answer is A.
generated_skill:
solution: Distance affects the strength of the magnetic force. When magnets are farther apart, the magnetic force between them is weaker. The magnets in Pair 2 are farther apart than the magnets in Pair 1. So, the magnetic force is weaker in Pair 2 than in Pair 1.
skill: Compare strengths of magnetic forces
id: 20075
lecture: A solution is made up of two or more substances that are completely mixed. In a solution, solute particles are mixed into a solvent. The solute cannot be separated from the solvent by a filter. For example, if you stir a spoonful of salt into a cup of water, the salt will mix into the water to make a saltwater solution. In this case, the salt is the solute. The water is the solvent. The concentration of a solute in a solution is a measure of the ratio of solute to solvent. Concentration can be described in terms of particles of solute per volume of solvent. concentration = particles of solute / volume of solvent
question: Which solution has a higher concentration of green particles?
choice: (A) neither; their concentrations are the same (B) Solution A (C) Solution B
context: The diagram below is a model of two solutions. Each green ball represents one particle of solute.
answer: B
rationale: A solution is made up of two or more substances that are completely mixed. In a solution, solute particles are mixed into a solvent. The solute cannot be separated from the solvent by a filter. For example, if you stir a spoonful of salt into a cup of water, the salt will mix into the water to make a saltwater solution. In this case, the salt is the solute. The water is the solvent. The concentration of a solute in a solution is a measure of the ratio of solute to solvent. Concentration can be described in terms of particles of solute per volume of solvent. concentration = particles of solute / volume of solvent In Solution A and Solution B, the green particles represent the solute. To figure out which solution has a higher concentration of green particles, look at both the number of green particles and the volume of the solvent in each container. Use the concentration formula to find the number of green particles per milliliter. Solution B has more green particles per milliliter. So, Solution B has a higher concentration of green particles. The answer is C.
generated_skill:
solution: In Solution A and Solution B, the green particles represent the solute. To figure out which solution has a higher concentration of green particles, look at both the number of green particles and the volume of the solvent in each container. Use the concentration formula to find the number of green particles per milliliter. Solution A has more green particles per milliliter. So, Solution A has a higher concentration of green particles.
skill: Compare concentrations of solutions
id: 20132
lecture: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is stronger when the magnets are closer together.
question: Think about the magnetic force between the magnets in each pair. Which of the following statements is true?
choice: (A) The magnetic force is stronger in Pair 1. (B) The strength of the magnetic force is the same in both pairs. (C) The magnetic force is stronger in Pair 2.
context: The images below show two pairs of magnets. The magnets in different pairs do not affect each other. All the magnets shown are made of the same material.
answer: C
rationale: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is stronger when the magnets are closer together. Distance affects the strength of the magnetic force. When magnets are closer together, the magnetic force between them is stronger. The magnets in Pair 1 are closer together than the magnets in Pair 2. So, the magnetic force is stronger in Pair 1 than in Pair 2. The answer is A.
generated_skill:
solution: Distance affects the strength of the magnetic force. When magnets are closer together, the magnetic force between them is stronger. The magnets in Pair 2 are closer together than the magnets in Pair 1. So, the magnetic force is stronger in Pair 2 than in Pair 1.
skill: Compare strengths of magnetic forces
id: 20381
lecture: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is weaker when the magnets are farther apart.
question: Think about the magnetic force between the magnets in each pair. Which of the following statements is true?
choice: (A) The strength of the magnetic force is the same in both pairs. (B) The magnetic force is weaker in Pair 1. (C) The magnetic force is weaker in Pair 2.
context: The images below show two pairs of magnets. The magnets in different pairs do not affect each other. All the magnets shown are made of the same material.
answer: B
rationale: Magnets can pull or push on each other without touching. When magnets attract, they pull together. When magnets repel, they push apart. These pulls and pushes between magnets are called magnetic forces. The stronger the magnetic force between two magnets, the more strongly the magnets attract or repel each other. You can change the strength of a magnetic force between two magnets by changing the distance between them. The magnetic force is weaker when the magnets are farther apart. Distance affects the strength of the magnetic force. When magnets are farther apart, the magnetic force between them is weaker. The magnets in Pair 2 are farther apart than the magnets in Pair 1. So, the magnetic force is weaker in Pair 2 than in Pair 1. The answer is C.
generated_skill:
solution: Distance affects the strength of the magnetic force. When magnets are farther apart, the magnetic force between them is weaker. The magnets in Pair 1 are farther apart than the magnets in Pair 2. So, the magnetic force is weaker in Pair 1 than in Pair 2.
skill: Compare strengths of magnetic forces