CBA 4 Science 2025 part 1

In 1980 the volcano found in Mount St. Helens erupted, since then scientists have been studying the repopulation of plant life in the area. Initially, wildflowers started to populate the region, followed by the emergence of shrubs and small trees. Scientists estimate that it may take several centuries for the area to evolve back into a forest  featuring fir and hemlock trees. These developments illustrate an example of-

• Humans damaging an ecosystem by eliminating wildflowers

• The decrease of genetic diversity in a plant species

• The development of a forest through ecological succession

• Biological evolution of flowers, shrubs and trees

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The diagram shows a plant cell with several of it structures labeled. 

Identify the cell structure that is responsible for storing food, water and waste.

Enter your answer

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Which of the following statements are true about hurricanes? Choose THREE correct answers.

• Hurricanes get stronger when they make landfall

• Hurricanes that originate in the Northwest Pacific are called typhoons

• Hurricanes are storm systems with high-pressure centers

• Hurricanes form over warm ocean water which provides them energy

• Hurricanes lose their strength when they move across land

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How does biodiversity contribute to the sustainability of an ecosystem?

• Biodiversity decreases the number of predators.

• Biodiversity provides a variety of species that can adapt to changes.

• Biodiversity increases the amount of sunlight in an ecosystem.

• Biodiversity reduces the need for water in an ecosystem.

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Aspen tree populations in the western United States are being devastated by an unidentified disease… This changed environment is impacting the wildlife that inhabits the area.

How will the stability of this ecosystem be impacted?

• The decrease in plant species will generate much more complex food webs.

• The disturbance to the ecosystem will decrease biodiversity leading to a decrease in this ecosystem’s stability.

• The disturbance to the ecosystem will increase biodiversity leading to decrease in this ecosystem’s stability.

• The decrease in biodiversity will increase food production within this ecosystem.

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Choose the correct terms to complete the statements below.

The illustration shows a chromosome that holds​ ​ (a)   which are​ accountable for encoding​ ​ (b)  

• genes
• inherited traits
• only dominant traits
• un-inherited traits
• learned behaviors
• innate behaviors

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Different conditions impact the stability of an ecosystem over time. When conditions change, primary or secondary succession can change an ecosystem. Write the letter of each answer in the correct column to describe primary succession and secondary succession. Each answer may be used more than once.

Soil formation begins​

Groups:

(a) Primary Succession

,

(b) Secondary Succession

• The number of species increase over time

• Begins with no organisms present

• The number of species increase over time.

• Begins with soil and organisms

• Begins after an ecosystem disruption

  
  Begins after an ecosystem disruption

• Soil formation begins

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What happens to the energy flow in a the food web shown when a natural disaster occurs?

• Only the top predators are affected

• Energy flow is disrupted, affecting all organisms in the web

• Only the primary producers are affected

• Energy flow remains unchanged

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Two different cell types are shown below. Identify each type of cell and the functions of each of the organelles that are labeled.  Move ONE correct answer to each box.                                                                   .

a

b

c

d

e

f

g

Animal cell

site for photosynthesis

energy production

contains genetic material

contains genetic material.

plant cell

energy production.

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Fires can devastate ecosystems, but they can also help them start to renew themselves over time. A fire burned part of a forest ecosystem as shown in the diagram. How does succession result in changes to the stability of an ecosystem? Complete the statements below.

Fire has disrupted an ecosystem, causing it to become ​ (a)   stable. Soil ​ (b)   and seeds will soon begin to grow. Over time, ​ (c)   organisms and species will be present and the ecosystem will become ​ (d)   ecologically stable.

• less
• is present
• more
• extra
• is not present
• fewer

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