Biology MCQs with answers Page - 60

In most ecosystems, the primary source of energy is the sun. Through the process of photosynthesis, plants, algae, and some bacteria convert solar energy into chemical energy, which is stored in the form of glucose. This energy is then passed through the food chain as organisms consume plants or other organisms for nourishment.

Here’s why the other options are incorrect:

• (A) Water: While water is crucial for life and photosynthesis, it does not provide the primary source of energy for ecosystems.
• (B) Carbon dioxide: Carbon dioxide is important for photosynthesis, but it is not a direct source of energy.
• (D) Soil: Soil provides nutrients, but it is not the primary source of energy in ecosystems.

Thus, the sun is the ultimate source of energy in most ecosystems.

Ethology is the scientific study of the typical behavior of organisms in their natural habitat. Ethologists observe and analyze how animals behave in their natural environments, focusing on aspects such as communication, social interactions, mating behavior, and survival strategies.

Here’s a breakdown of the other options:

• (A) Euthenics: This refers to the study of improving human well-being by improving environmental factors like nutrition and living conditions, rather than the behavior of organisms.
• (B) Eugenics: This is the study of improving the genetic quality of the human population, often associated with controversial and unethical practices.
• (D) Ethnology: This is the study of cultures and societies of humans, focusing on their customs, traditions, and social behaviors, not animal behavior.

Therefore, Ethology is the correct term for the study of behavior in natural settings.

All of the examples listed involve parasitism, which is a type of symbiotic relationship where one organism benefits at the expense of the other.

• (A) Leeches consume blood of their host: Leeches are parasitic because they feed on the blood of their host, such as mammals, without providing any benefit to the host.
• (B) Ticks that live on dogs: Ticks are also parasitic, as they attach to dogs (or other animals) and feed on their blood, often causing harm.
• (C) Aphid insects eat the sap of the host plant: Aphids feed on the sap of plants, which can weaken the plant and may even lead to diseases, making this a parasitic relationship as well.

In all these cases, the parasite benefits by taking resources from the host, while the host is harmed, making these examples of parasitism.

Commensalism is a type of symbiotic relationship where one species benefits from the interaction, while the other species is neither helped nor harmed. Essentially, one organism gains some advantage (like food or shelter), while the other organism is unaffected.

Here’s a quick breakdown of the other options:

• (A) Predation: Involves one species (the predator) benefiting by killing and eating another species (the prey), which is harmed.
• (C) Competition: Occurs when two species vie for the same resources (e.g., food, space), leading to harm for both as they compete.
• (D) Parasitism: Involves one species benefiting at the expense of the other, causing harm to the host.

Therefore, commensalism is the correct term for the interaction where one species benefits and the other is unaffected.

• Statement 1: "Different plant species grow together" refers to a diverse range of plant species growing in the same area, which is characteristic of equatorial moist evergreen forests. These forests have a high level of biodiversity.
• Statement 2: "Light cannot penetrate into the lower strata full of undergrowth" suggests that the canopy of trees is dense and thick, preventing light from reaching the forest floor. This is a feature of equatorial moist evergreen forests, where the canopy is typically dense, and the understory is shaded and full of undergrowth.

In equatorial moist evergreen forests, such as those in the Amazon or Congo basins, the combination of diverse plant species and a dense canopy that blocks light from reaching the forest floor fits the description provided in the question.

The other options do not fully match these characteristics:

• (B) Tropical deciduous: These forests shed leaves during dry seasons, unlike evergreen forests, and usually have more sunlight reaching the ground during the dry season.
• (C) Mediterranean: Characterized by hot, dry summers and mild, wet winters, typically with shrubs and small trees, not dense canopies or constant undergrowth.
• (D) Warm temperate broad-leaved deciduous: These forests have seasonal leaf shedding, and while they may have some shading, they do not have the same level of dense undergrowth or biodiversity as equatorial forests.

Thus, the correct answer is (A) Equatorial moist evergreen.

Ecology is the branch of biology that deals with the study of the relationship between organisms and their environment. It focuses on how organisms interact with each other and with their physical surroundings, including factors like climate, soil, water, and other living organisms.

Here’s why the other options are incorrect:

• (B) Taxonomy: This is the branch of biology that deals with the classification, identification, and naming of organisms.
• (C) Evolution: This is the study of how species change over time through processes like natural selection and genetic drift.
• (D) Genetics: This is the study of heredity and the variation of inherited characteristics in organisms.

Therefore, ecology is the correct answer, as it specifically addresses the interactions between organisms and their environment.