Question
The graph illustrates the relationship between atmospheric carbon dioxide levels and global temperature anomalies (deviations from average global temperatures) from the Industrial Revolution through to 2017.
Which statement explains the correlation between atmospheric carbon dioxide concentration and temperature shown in the graph?
A. Carbon dioxide heats up the surface of the Earth.
B. More short-wave radiation bounces back to space, causing warmer seasons.
C. Less long wave radiation can escape the atmosphere, heating up the Earth.
D. Less radiation is emitted by the Earth’s surface, increasing seasonal fluctuations.
▶️Answer/Explanation
Answer: C. Less long wave radiation can escape the atmosphere, heating up the Earth.
Explanation:
Carbon dioxide (CO₂) is a greenhouse gas. It traps long wave (infrared) radiation that the Earth emits after absorbing sunlight. This trapped heat causes the greenhouse effect, which raises Earth’s average temperature. The graph showing a rise in both CO₂ levels and temperature anomalies demonstrates this positive correlation.
Option Evaluation:
A. Incorrect – CO₂ itself doesn’t directly heat the Earth’s surface. It works by trapping heat that would otherwise escape into space.
B. Incorrect – Short wave radiation (from the sun) mostly enters the atmosphere. It’s the long wave radiation, re-emitted by the Earth, that gets trapped, not bounced back.
C. Correct – This accurately describes the greenhouse effect. CO₂ causes less long wave radiation to escape, trapping heat and warming the planet.
D. Incorrect – The Earth still emits radiation. The issue is not about seasonal fluctuations or reduced emission, but rather the trapping of the emitted long wave radiation by greenhouse gases.
Question
The diagram shows flows of energy and matter in an ecosystem. What do the letters P, Q and R represent?
▶️ Answer/Explanation
Ans. C
Diagram breakdown:
- P → Producers (energy): P is the energy input to producers.
- Producers → Consumers: Energy and matter flow from producers to consumers.
- Consumers → Decomposers: Energy and matter pass from consumers to decomposers.
- Decomposers → Producers (matter): This shows recycling of nutrients.
Q is connected back to producers and consumers with energy arrows.
R is connected to producers with matter arrows.
What do these flows represent?
P: Energy input to producers → light
Q: Energy lost from system → heat
R: Matter recycled to producers from decomposers → inorganic nutrients
Why others are incorrect:
- A: Water vapour and nitrates don’t match the energy flow.
- B: Chemical energy is stored in producers, but the initial energy source is light.
- D: Chemical energy → carbon dioxide → glucose mixes up matter and energy flows.
Question
The three-toed sloth, Bradypus variegatus, lives in tree tops where it feeds on leaves. It also feeds on algae and fungi which live in its fur.
In which trophic group should the three-toed sloth be classified?
A. Autotroph
B. Consumer
C. Detritivore
D. Saprotroph
▶️ Answer/Explanation
Answer: B. Consumer
Explanation:
Trophic groups classify organisms by how they obtain energy:
- Autotrophs make their own food (e.g., plants).
- Consumers eat other organisms.
- Detritivores feed on dead material but ingest it (e.g., earthworms).
- Saprotrophs secrete enzymes on dead matter and absorb nutrients (e.g., fungi).
Option Evaluation:
A. Incorrect – Sloths are not autotrophs; they don’t photosynthesize.
B. Correct – Sloths consume leaves and small organisms like algae and fungi. That makes them primary or secondary consumers depending on what they eat.
C. Incorrect – Detritivores eat dead material, which is not the sloth’s main diet.
D. Incorrect – Saprotrophs break down dead organic matter externally. Sloths don’t do this.
Question
Which processes occur in an ecosystem?
I. Biomass increases in each successive trophic level.
II. Inorganic nutrients are recycled.
III. Chemical energy is stored in carbon compounds.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
Answer: C. II and III only
Explanation:
- I. Biomass increases at each trophic level – False. Biomass decreases at each level due to energy loss (e.g., through heat, respiration).
- II. Inorganic nutrients are recycled – True. Elements like nitrogen and phosphorus are cycled through biotic and abiotic parts of ecosystems.
- III. Chemical energy is stored in carbon compounds – True. Energy from the sun is stored in glucose and other carbon-based molecules via photosynthesis.
Option Evaluation:
A. Incorrect – I is false, so this combination is incorrect.
B. Incorrect – I is false, so this option is also wrong.
C. Correct – Both II and III are true. Nutrients are recycled and energy is stored in carbon compounds.
D. Incorrect – I is false, so all three statements cannot be correct.
Question
A hummingbird is shown visiting a large flower.
What makes this a mutualistic relationship?
A. The bird feeds on nectar and transfers pollen to the stamen of a flower of the same species.
B. The bird obtains nutrients, and the plant is assisted with pollination for sexual reproduction.
C. The bird requires pollen as a protein source and, while obtaining this, disperses seeds for the plant.
D. The bird transfers pollen to the stigma of flowers of a different species while feeding.
Answer/Explanation
Answer: B. The bird obtains nutrients, and the plant is assisted with pollination for sexual reproduction.
Explanation:
Mutualism is a relationship where both organisms benefit. The hummingbird gets nectar (its food), and the flower benefits through pollination, which helps with reproduction.
Option Evaluation:
A. Incorrect – Close, but a technical error: pollen is transferred to the stigma, not the stamen (which produces pollen).
B. Correct – This correctly explains mutualism: the bird gets food, and the plant gets help with sexual reproduction via pollination.
C. Incorrect – Hummingbirds don’t eat pollen for protein (that’s more common in bees). Also, they do not disperse seeds; they transfer pollen.
D. Incorrect – Transferring pollen to a different species’ flower does not help pollination. For successful reproduction, pollen must reach the same species.
Question
Hummingbirds eat flower nectar and small insects. To which nutritional group do they belong?
Autotrophs
Consumers
Detritivores
Saprotrophs
Answer/Explanation
Answer: B. Consumers
Explanation:
Nutritional groups describe how organisms obtain food:
- Autotrophs make their own food.
- Consumers eat other organisms.
- Detritivores eat dead material by ingesting it.
- Saprotrophs externally digest dead material.
Correct Answer: Consumers – Hummingbirds consume nectar and small insects, both of which are organic sources of food, so they are heterotrophic consumers.