Biology MCQs
Topic Notes: Biology
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
In which ecosystem are secondary and tertiary consumers typically absent or minimal?
Answer:
Cropland ecosystem
A cropland ecosystem is an artificial, human-managed environment. Because farmers actively remove pests and predators to protect crops, the natural food web is simplified. Consequently, higher trophic levels like secondary and tertiary consumers are often excluded or significantly reduced compared to natural ecosystems like forests or grasslands.
2
Which of the following ecosystems is characterized by the absence of primary producers, relying entirely on detritus for energy?
Answer:
Abyssal depths of sea
In the abyssal depths of the ocean, sunlight cannot penetrate, making photosynthesis impossible. Consequently, there are no primary producers (plants or algae). The ecosystem relies on 'marine snow'—organic detritus falling from the upper layers—to support consumers and decomposers living in these extreme, dark environments.
3
Which organisms occupy the highest trophic level in a food chain and are typically classified as top carnivores?
Answer:
Tertiary consumers
In a standard food chain, tertiary consumers are organisms that feed on secondary consumers. Because they occupy the highest trophic level and have few or no natural predators, they are referred to as top carnivores or apex predators within that specific ecosystem.
4
In an ecological food web, how are omnivores, which consume both plant and animal matter, typically classified?
Answer:
Secondary consumers
Omnivores occupy multiple trophic levels. While they act as primary consumers when eating plants, they are classified as secondary consumers when they consume herbivores or other primary consumers. In many ecological models, they are categorized as secondary consumers because they derive energy from higher trophic levels in addition to primary producers.
5
What is the definition of bio-magnification?
Answer:
Increasing a number of pesticides in the organisms of successive tropic level
Bio-magnification refers to the increasing concentration of persistent substances, such as pesticides or heavy metals, in the tissues of organisms at each successive trophic level of a food chain. This occurs because these substances are not easily metabolized or excreted, leading to higher concentrations in top predators.
6
According to Odum, which conditions are essential for maintaining biological energy flow in estuaries?
Answer:
1, 2, 3 and 4 are true
Odum identified several key factors for estuarine productivity: tidal flushing removes metabolic waste, diverse species ensure continuous photosynthesis, the estuary acts as a nutrient trap, and the proximity of autotrophs and heterotrophs facilitates efficient energy cycling.
7
Which group of organisms occupies the first trophic level in an ecosystem?
Answer:
Green plants
In an ecosystem, the first trophic level is composed of primary producers. These are autotrophic organisms, primarily green plants, algae, and some bacteria, that convert solar energy into chemical energy through photosynthesis. They provide the foundational energy source for all subsequent trophic levels, including herbivores and carnivores.
8
What is the process by which agrochemicals like pesticides and fungicides accumulate in organisms and disrupt food chains?
Answer:
Biomagnification
Biomagnification refers to the increasing concentration of persistent toxic substances, such as pesticides, at each successive trophic level of a food chain. Because these chemicals are not easily metabolized or excreted, they accumulate in the tissues of organisms, reaching dangerous levels in top predators, which can lead to severe ecological disruption and health issues.
9
Who is credited with first introducing the term 'plankton' to the scientific community in 1887?
Answer:
V. Hensen
Victor Hensen, a German marine biologist, coined the term 'plankton' in 1887. He used it to describe the diverse collection of organisms that drift or float in water bodies, unable to swim against the current, which is a foundational concept in aquatic ecology and oceanography.
10
Which of the following ecological classifications is incorrectly matched?
Answer:
Herbivore ⟺ Secondary consumer
In ecological trophic levels, autotrophs are producers, heterotrophs are consumers, and saprotrophs are decomposers. Herbivores are classified as primary consumers because they feed directly on producers. Secondary consumers are organisms that eat primary consumers (carnivores or omnivores). Therefore, matching herbivores with secondary consumers is incorrect.