Context:
Scientists have recently discovered that prokaryotes are highly resilient to climate change, which may lead to their increased dominance in marine environments.
Recent Findings
- Resilience: Prokaryotes are resilient to climate change, potentially dominating marine environments.
- Impact: Could reduce fish availability and hamper ocean’s carbon absorption ability.
Prokaryotes:
- Definition: Single-cell organisms lacking a nucleus and other membrane-bound organelles.
- Types: Includes bacteria and archaea.
- Structure: Small, single-celled with a simple structure; oldest cell-based lifeforms on Earth.
- Organelles: Surrounded by a plasma membrane; no internal membrane-bound organelles.
- Size: Typically 0.1–5.0 micrometers (μm) in diameter; smaller than eukaryotic cells (10–100 μm).
- Adaptability: Thrive globally on land and in water, from tropics to poles.
- Significance: Crucial in food chains, supporting nutrient needs of fish.
Carbon Emission:
- Growth: Marine prokaryotes grow fast, emitting significant carbon.
- Emission: Produce about 20 billion tonnes of carbon annually to 200 meters ocean depth, double that of humans.
- Balance: Carbon output balanced by phytoplankton through photosynthesis.
Eukaryotes:
- Includes plants, animals, and fungi.
- Have a well-defined nucleus and membrane-enclosed organelles.
- Can be unicellular or multicellular.
- Possess multiple chromosomes.
- Plant and animal cells differ:
- Plant cells have cell walls, plastids, and a large central vacuole.
- These features are absent in animal cells.
Source: TH
Previous Year Question
Which of the following statements are correct regarding the general difference between plant and animal cells?
1. Plant cells have cellulose cell walls while animal cells do not.
2. Plant cells do not have a plasma membrane, unlike animal cells which do.
3. Mature plant cell has one large vacuole whilst animal cell has many small vacuoles.
Select the correct answer using the code given below:
[UPSC Civil Services Exam – 2020 Prelims]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c)
Explanation:
Statement 2 is not correct:
The plasma membrane is present in both plant cells and animal cells.
