Ans: A

Exp:

Ecological Succession is the progressive series of changes that lead to establishment of a relatively stable climax community.

Statement 1 is correct: It is characterized by increased  productivity, the shift of nutrients from the reservoirs, increased the diversity of organisms with increased niche development and a gradual increase in the complexity of food webs.

Statement 2 is incorrect: Examples of areas where primary  succession occurs are newly cooled lava, bare rock, newly created pond or reservoir, etc. Secondary succession is the sequential development of biotic communities after

the complete or partial destruction of the existing community. Secondary succession starts on a well-  developed soil already formed at the site. Thus secondary succession is relatively faster as compared to primary succession which may often require hundred of years

Statement 3 is correct: Succession which starts in areas where  no living organisms ever existed is called primary succession. In primary succession on a terrestrial site, the new site is first colonized by a few hardy pioneer species that are often microbes, lichens, and mosses.

Ans: C

Exp:

Indicator species are the ones whose presence or abundance reflects the environmental condition. They serve as early warning mechanisms or signals as they are sensitive to environmental conditions. For example, certain types of aquatic insects are often used as indicators of water quality. If pollution levels in a river increase, these indicator species may disappear or show signs of stress before larger ecological problems become apparent, alerting scientists and conservationists to potential issues.

Other significant classifications of the species are:

• Endemic species are plant and animal species that are found in a particular geographical region and nowhere else in the world. Eg. Lion Tailed Macaque, Nilgiri Tahr , kashmiri stag or Hangul are some of the endemic species of India.
• A keystone species is an organism that helps hold the system together. Without its keystone species, ecosystems would look very different. Some ecosystems might not be able to adapt to environmental changes if their keystone species disappeared. Eg. Top Level predators such as Lion, Tiger comes under the list of keystone species. Bees are also an example of keystone species, in plants Mangrove trees are an example of keystone species in an aquatic ecosystem.
• Invasive alien species are plants, animals, pathogens and other organisms that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health. In particular, they impact adversely upon biodiversity, including decline or elimination of native species – through competition, predation, or transmission of pathogens – and the disruption of local ecosystems and ecosystem functions. Eg. Water hyacinth, Prosposis Juliflora in India.

Ans: A

Exp:

Statement 1 is incorrect: Mangroves are practically evergreen with thick leathery leaves. Their leaves are generally small to reduce transpiration losses. 

Statement 2 is incorrect: Mangrove trees, growing in anoxic unstable sediments, with incredibly shallow root systems (no deeper than 30 below the soil surface) still maintain their vertical stems, withstand hurricanes, and storm surges, and protect each other.

Statement 3 is correct: Saline water, unconsolidated saline soil with little or no oxygen is not a conducive environment for seeds to germinate and establish. To overcome this, mangrove species have a unique way of reproduction, which is generally known as vivipary. In this method of reproduction, seeds germinate and develop into seedlings while the seeds are still attached to the parent tree. 

Ans: B

Exp:

Statement 1 is correct: Coral reefs support upto 25% of the ocean’s fishes. Fishes and other organisms shelter, find food, reproduce, and rear their young in the many nooks and crannies formed by corals. 

Statement 2 is incorrect: However, the reef-building corals that rely on a symbiotic relationship with algae need shallow, clear water allowing light penetration for photosynthesis. They also require tropical or sub-tropical temperatures, which exist in a band 30 degrees north to 30 degrees south of the equator.

Statement 3 is correct: Many coral reef animals play important roles within coral reef ecosystems. For example, herbivores like parrotfish and sea turtles graze on algae and help keep algae populations under control. 

These herbivorous fish and other marine animals play a crucial role in maintaining the balance of the coral reef ecosystem and considered good for the growth of Coral Reef structure.

Ans: A

Exp:

Statement 1 is correct: Kelp are large brown algae (Phaeophyta) that live in cool, relatively shallow waters close to the shore. There are about 30 different species of kelp worldwide. They grow in dense groupings much like a forest on land, and are found predominantly along the Pacific coast from Alaska to parts of Baja California. 

Statement 2 is incorrect: Kelp thrives in cold, nutrient-rich waters. Generally , kelps live further from the tropics than coral reefs, mangrove forests, and warm-water seagrass beds, so kelp forests do not overlap with those systems.