Olympiad Test: Nutrition In Plants And Animals -2 - Class 7 MCQ

To determine the number of teeth an adult has, we need to consider the permanent dentition.
The permanent dentition consists of 32 teeth, which are divided into four types: incisors, canines, premolars, and molars.
- Incisors: There are eight incisors in total, four in the upper jaw (two central incisors and two lateral incisors) and four in the lower jaw (two central incisors and two lateral incisors).
- Canines: There are four canines, two in the upper jaw (one on each side) and two in the lower jaw (one on each side).
- Premolars: There are eight premolars, four in the upper jaw and four in the lower jaw. They are located between the canines and molars.
- Molars: There are twelve molars, including four third molars (also known as wisdom teeth). The molars are located at the back of the mouth.
Adding up the numbers, we have:
8 incisors + 4 canines + 8 premolars + 12 molars = 32 teeth
Therefore, the correct answer is option D: 32.

There are four major types of teeth: incisor, canines, premolars and molars.

• Incisors: They are needed for biting and cutting food.
• Canines: They are needed for tearing food.
• Premolars: They are needed to tear and crush food.
• Molars: They are needed to chew, crush and grind food.

Cuscuta, commonly known as dodder, is a parasitic plant that lives on various host plants. Among the options provided

Why do xerophytes have very small leaves or spines?
Xerophytes are plants that are adapted to survive in dry and arid conditions. They have evolved various strategies to minimize water loss and maximize water retention. One of these adaptations is the development of very small leaves or spines. This adaptation serves the following purposes:
1. Reducing loss of water:
- Xerophytes live in environments where water is scarce, so it is essential for them to minimize water loss through transpiration.
- Small leaves or spines have a smaller surface area compared to larger leaves, reducing the surface area available for transpiration.
- This helps to conserve water and prevent excessive dehydration.
2. Conserving water:
- Xerophytes often have specialized tissues or structures that help in water retention.
- By reducing the size of leaves or having spines, xerophytes can allocate more resources towards developing these specialized tissues or structures.
- This enables them to store water more efficiently and survive in water-limited environments.
3. Minimizing exposure to harsh conditions:
- Xerophytes inhabit environments with extreme temperatures, strong winds, and intense sunlight.
- Small leaves or spines help to reduce the overall volume and weight of the plant, making it more resistant to damage caused by these harsh conditions.
- This adaptation allows xerophytes to withstand strong winds without being uprooted and prevents excessive evaporation from the plant's surface.
4. Preventing herbivory:
- Some xerophytes have spines instead of leaves to deter herbivores from feeding on them.
- Spines are sharp and can be a physical barrier, preventing animals from accessing the plant's nutrients and water content.
- This adaptation increases the plant's survival chances in arid environments where food sources are limited.
In summary, xerophytes have very small leaves or spines primarily to reduce water loss, conserve water, minimize exposure to harsh conditions, and prevent herbivory. These adaptations enable them to thrive in dry and arid habitats.

Sunlight is essential for photosynthesis as the plant is kept in dark room for a week. There is a lack of sunlight, hence photosynthesis has not taken place. 

Pulp is the soft material in the tooth. It is richly supplied with blood vessels and nerves. 

Dentine is the calcified tissue of the body, is one of the components of the teeth along with enamel, cementum and pulp. It is generally surrounds the entire pulp is a covering beneath the enamel. 70% of the weight of dentine is made up of mineral hydroxylapatitie, while 20% is organic material and the rest 10% is water.

The term dentistry comes from dentist, which comes from French dentiste, which comes from the French and Latin words for tooth. The term for the associated scientific study of teeth is odontology – the study of the structure, development, and abnormalities of the teeth.

Adaptations developed by desert plants to manage water scarcity:

• Modified leaves: Desert plants often have leaves that are modified into spines. These spines help reduce the surface area of the leaves, minimizing water loss through transpiration.


• Reduced leaf shedding: Some desert plants may retain their leaves throughout the year or shed them only during specific seasons when water availability is higher.


• Storing water: Desert plants have adaptations to store water in their stems, trunks, or leaves. This allows them to survive during periods of drought.


• Reduced stomata: Stomata are the pores through which water is lost via transpiration. Desert plants often have fewer stomata or have them located in protected areas, reducing water loss.


• Deep root systems: Desert plants develop long and extensive root systems to tap into underground water sources. Some plants may also have shallow roots that spread out to quickly capture rainfall.


• Waxy or hairy coatings: Some desert plants have a waxy or hairy coating on their leaves to reduce water loss through evaporation.

Therefore, the correct adaptation developed by desert plants to manage water scarcity is their leaves are modified into spines (Option B).