Coordination, Defense & Reproduction — Chapter Practice, Grade 7

Five focused units, a three-session investigation, chapter review, and chapter quiz.

Problem 1

Is a receptor alone the whole sensory experience?
Answer and explanation

No. Signals and processing contribute to perception, interpretation, and response.

Problem 2

Does seeing a ball mean the ball travels through a nerve?
Answer and explanation

No. Signals carry information about detected light; the physical ball does not move through the nerve pathway.

Problem 3

Why is “the brain never learns about a reflex” too strong?
Answer and explanation

A reflex can begin without conscious decision, while related information can still reach the brain.

Problem 4

Can one reaction-time score establish overall intelligence?
Answer and explanation

No. It measures one task under particular conditions and can be affected by several non-intelligence factors.

Problem 5

Illustrative timing trials are 0.20, 0.25, and 0.30 seconds for one defined task. A draft labels the mean a complete measure of the person’s intelligence. Calculate mean and range, describe the measured pathway in general, and correct the claim.
Answer and explanation

Mean response time is 0.25 s and numerical range is 0.10 s. A stimulus-response task involves detection, processing, and action plus measurement conditions. These values cannot establish overall intelligence or health; attention, equipment, and task demands also matter. They describe only the supplied fictional trials.

Mean: 0.75/3=0.25 s.

Range: 0.30−0.20=0.10 s.

Separate the task measure from an unsupported personal conclusion.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

Why could different task instructions change a response-time comparison?
Answer and explanation

They can change what must be detected, interpreted, or done. Comparable instructions and timing methods are needed before comparing outcomes.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which is a stimulus in a light-response model?
  1. A change in light
  2. The whole graph caption
  3. A claim of intelligence
  4. The mean alone
Answer and explanation

A change in light

The light change is the input that relevant receptors can detect.

Problem 8

Find the mean of 0.3, 0.4, and 0.5 seconds.
Answer and explanation

0.4 s

(0.3+0.4+0.5)/3=1.2/3=0.4 s.

Problem 9

Does homeostasis require the same number at every instant?
Answer and explanation

No. Regulation can maintain functioning ranges while values vary with conditions.

Problem 10

What makes a response negative feedback in this model?
Answer and explanation

Its effect opposes the initial deviation in the regulated condition.

Problem 11

Why should a hormone model show responsive target cells?
Answer and explanation

Cells differ in their ability to respond to a particular signal; transport everywhere does not mean the same response everywhere.

Problem 12

Does return toward a model range identify the sole cause?
Answer and explanation

No. Several processes can affect the quantity; the record and mechanism must be assessed together.

Problem 13

Illustrative artificial-system record: a quantity rises from 20 to 24 units; a detector activates an output that lowers it to 21. The stated working range is 19–22 units. Explain the direction of feedback, the final relation to the range, and why these are not human clinical values.
Answer and explanation

The response opposes the rise, so it represents negative feedback. The final 21 lies within the stated working range. The units and thresholds are invented for an artificial system; they do not evaluate a learner’s body. The model illustrates a relationship while omitting the complexity of living regulation.

Identify the initial rise.

Connect the activated output with the opposing decrease.

Compare 21 with the invented range.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 14

A student says “negative feedback is bad feedback.” Correct the terminology.
Answer and explanation

Negative describes opposition to a deviation. It does not label the process morally or medically harmful.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 15

Which illustrates negative feedback?
  1. A response counteracts the original rise
  2. A number is called negative
  3. Every signal stops
  4. The deviation is always amplified
Answer and explanation

A response counteracts the original rise

The defining relationship is opposition to the initial deviation.

Problem 16

A model quantity rises to 18 units, then falls to 13. Find the response-period change.
Answer and explanation

-5 units

13−18=−5 units.

Problem 17

Are all bacteria disease-causing?
Answer and explanation

No. Bacteria have diverse roles, including many that are harmless or beneficial in particular contexts.

Problem 18

Does an entry barrier prove no agent can ever enter?
Answer and explanation

No. It can reduce entry, while effectiveness depends on conditions and other pathways.

Problem 19

Why is a matching-shape model limited?
Answer and explanation

It illustrates recognition but omits molecular complexity, multiple defense pathways, and real organism variation.

Problem 20

Does response to Agent A establish the same response to Agent B?
Answer and explanation

No. Specific recognition and other conditions can differ; B needs its own evidence.

Problem 21

Illustrative model: a response recognizes Symbol A; Symbol B differs; after repeated A exposure the model response begins faster. No clinical records are represented. Explain specific recognition and memory, distinguish the observation from a universal protection claim, and state a model limit.
Answer and explanation

The model illustrates target-specific recognition and a memory-related faster response to A. It does not establish an identical response to B or guaranteed protection in a real person. Matching symbols simplify molecular interactions and omit many defense pathways. The supplied pattern is educational evidence about the model, not a clinical assessment.

Identify the repeated target A.

Compare response timing under the stated model.

Avoid assigning the same result to B or every real infection.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 22

Why should a decomposition bacterium not automatically be labeled a harmful pathogen?
Answer and explanation

Its role depends on organism and context. Decomposition can recycle matter; being microscopic or bacterial does not by itself establish disease-causing activity.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 23

Which statement is supported?
  1. Every bacterium is harmful
  2. Viruses depend on host cells for replication
  3. Antibodies are whole organs
  4. Recognition of A proves universal protection
Answer and explanation

Viruses depend on host cells for replication

Viruses require suitable host-cell processes; bacterial roles and defense outcomes vary.

Problem 24

Why do the supplied symbols not justify a treatment recommendation?
Answer and explanation

They omit real agents, physiology, history, and clinical evidence. They illustrate a recognition concept rather than an actual health decision.

Problem 25

Does asexual reproduction forbid all variation?
Answer and explanation

No. Mutations and environmental effects can produce differences, even when offspring share much inherited material.

Problem 26

Is fertilization the same event as every later cell division?
Answer and explanation

No. Fertilization combines gametes; later divisions and development produce and organize cells.

Problem 27

Why is egg count not the same as successful adult offspring?
Answer and explanation

Some eggs may not be fertilized or survive development, and later survival and reproduction depend on conditions.

Problem 28

Can a reproductive diagram establish personal family information?
Answer and explanation

No. It describes a general process and should not be used to infer or demand a learner’s private history.

Problem 29

Illustrative organisms: A produces new individuals from parent tissue without gamete fusion; B begins with fusion of two gametes. A later develops one new mutation. Classify the mechanisms, explain how A can vary, and distinguish offspring production from successful reproduction over a life cycle.
Answer and explanation

A represents asexual reproduction and B sexual reproduction. A’s new mutation shows that asexual offspring are not guaranteed identical in every detail. The records describe production mechanisms, but later survival and reproductive success depend on development and conditions. More information is needed to compare outcomes, not merely count starting cells.

Identify no fusion in A and fusion in B.

Connect A’s new mutation with variation.

Consider later survival and reproductive stages.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 30

Two sexual offspring share parents but differ in traits. Does that by itself contradict inheritance?
Answer and explanation

No. They can receive different combinations of inherited material and experience different environments. Sexual inheritance is not an exact visual blend.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 31

What distinguishes the studied sexual reproduction model?
  1. Gamete fusion
  2. Every offspring is identical
  3. No inherited material
  4. Only one possible environment
Answer and explanation

Gamete fusion

Sexual reproduction involves gamete fusion; later development and conditions also affect outcomes.

Problem 32

A supplied record has 30 fertilized eggs from 50 eggs. What percent was fertilized?
Answer and explanation

60 %

30/50×100=60%; this does not give later survival.

Problem 33

Does observing a pollinator visit prove viable seeds formed?
Answer and explanation

No. The visit is one stage; transfer, compatibility, fertilization, and development need further evidence.

Problem 34

Why can early germination occur before a seedling has green leaves?
Answer and explanation

The seed can use stored resources and cellular respiration to support initial growth.

Problem 35

Does moving a seed automatically create a mutation?
Answer and explanation

No. Location changes environmental conditions; mutation is a change in genetic material and is a different process.

Problem 36

Why should the denominator include all tested seeds?
Answer and explanation

It defines success relative to the original sample; excluding failures would inflate the reported germination percentage.

Problem 37

Illustrative seven-day data: Treatment A has 18 germinated seeds of 20; B has 12 of 20. Species and other conditions are stated matched; the treatment is water amount. Calculate both percentages, describe the measured difference, and qualify the claim about lifelong plant success.
Answer and explanation

A has 90% germination and B 60%, a 30-percentage-point difference in this illustrative comparison. It supports a treatment-related germination question under the matched conditions, but does not establish adult survival, universal species response, or every causal detail. Replicate independent groups and record later growth separately.

A: 18/20×100=90%.

B: 12/20×100=60%.

Difference is 30 percentage points.

Limit the claim to the stipulated germination interval.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 38

Why is the same germination treatment not automatically best for every plant species?
Answer and explanation

Species can have different requirements and tolerances. Evidence from one species and interval needs qualification before generalizing.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 39

Which is pollination?
  1. Pollen transfer
  2. Every seed’s first leaf
  3. DNA duplication
  4. All adult survival
Answer and explanation

Pollen transfer

Pollination is pollen transfer; fertilization and development are subsequent distinct processes.

Problem 40

Eight of ten seeds germinate. Find germination percentage.
Answer and explanation

80 %

8/10×100=80%.

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