Explain limit of tolerance with the help of an example.

The number of snails (Cepaea nemoralis) eaten by birds was counted during late spring (days 1 to 10) and early summer (days 10 to 20), when the trees turn greener. More green snails are eaten when the background is brown and more brown snails are eaten when the background is green.

What statement refers to green and brown snails?

Lettuce coral is the dominant coral species in shallow semi-exposed reefs in the Southern Caribbean Sea. Colonies of $U$. Tenuifolia were classified according to the colony size into small, medium and large. The number of colonies according to their size were recorded three times, starting in spring of the first year, then autumn of the first year and ending in spring of the second year in a location in the Southern Caribbean. Suggest one reason for the change in population of small and medium corals.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Scientists investigated the pollination of four species of plants. Each of the species was treated in three ways: some plants had their flowers covered to exclude pollinators, other plants were not manipulated, allowing birds to pollinate them, and a third group was pollinated by hand using a paintbrush. The percentage of the total flowers that developed into fruit was recorded. 

Which species of plant is most efficiently pollinated by birds? 

Lettuce coral (Undaria tenuifolia) is the dominant coral species in shallow semi-exposed reefs in the Southern Caribbean Sea. Colonies of $U$. tenuifolia were classified according to the colony size into small, medium and large. The number of colonies according to their size were recorded three times, starting in spring of the first year (1), then autumn of the first year (2) and ending in spring of the second year (3) in a location in the Southern Caribbean. Describe how bleaching is an indication of stress on corals.

The number of snails (Cepaea nemoralis) eaten by birds was counted during late spring (days 1 to 10) and early summer (days 10 to 20), when the trees turn greener. More green snails are eaten when the background is brown and more brown snails are eaten when the background is green.

This pattern occurs continually throughout the years. What is a probable outcome? 

The table shows the number of plants of each species counted in a sand dune.

(b) Comment on the richness and evenness of this sand dune community.

The sand dune community was compared with that of a forest where 240 organisms were counted in a total of 10 species. The Simpson diversity index of this forest was 14.