All questions of Animal Life Cycles for Grade 3 Exam

Why do birds sit on their eggs?

Birds are unique creatures that lay eggs instead of giving birth to live young. After laying eggs, they sit on the eggs for a period of time before they hatch into young ones. This behavior of birds is known as incubation, and it serves a very important purpose.

Keeps the eggs warm

The primary reason why birds sit on their eggs is to keep them warm. Eggs need a constant temperature to develop properly, and the warmth provided by the bird's body is essential for the eggs to hatch. The body heat of the bird helps to regulate the temperature of the eggs, ensuring that they are neither too hot nor too cold. If the eggs get too cold, the embryos inside can die, and if they get too hot, they can also die.

Protect the eggs

Another reason why birds sit on their eggs is to protect them from predators. When the eggs are left unattended, they are vulnerable to being eaten by other animals. By sitting on the eggs, the bird can keep them safe from predators.

Ensure the eggs are healthy and strong

Birds also sit on their eggs to ensure that the embryos inside are healthy and strong. By sitting on the eggs, the bird can sense any problems with the eggs, such as if they are not developing properly or if there are any cracks in the shells. The bird can also turn the eggs to ensure that the embryos are getting oxygen and nutrients evenly.

Conclusion

In conclusion, birds sit on their eggs for several reasons, including keeping them warm, protecting them from predators, and ensuring that the embryos inside are healthy and strong. This behavior is essential for the survival of the species, and it is fascinating to see how birds use their instincts to care for their young even before they hatch.

Tadpoles have tails and also fishes have a tail

Maintaining and Increasing Animal Numbers:
Reproduction is a vital process for animals as it serves several important purposes. It allows animals to maintain their population size, increase their numbers, and maintain the balance of nature. Let's explore each of these reasons in detail:

Maintaining Population Size:
- Animals need to reproduce to maintain their population size. If animals do not reproduce, their numbers will gradually decrease over time due to natural factors such as predation, disease, and death. Reproduction ensures that new individuals replace the ones lost, thereby sustaining the population.

Increasing Population Size:
- Reproduction is also necessary for animals to increase their numbers. By giving birth to offspring, animals can expand their population and occupy new habitats. This is particularly important for species that have experienced a decline in numbers or are at risk of extinction. Reproduction helps to replenish and restore their population size.

Maintaining the Balance of Nature:
- Reproduction plays a crucial role in maintaining the balance of nature. Each animal species has a specific role or niche in the ecosystem, and their numbers need to be balanced for a healthy and functioning ecosystem.
- Predators and prey need to maintain a balance to avoid overgrazing or overpopulation of certain species. Reproduction ensures that there are enough individuals to fulfill these roles and that the ecosystem remains stable and sustainable.

Summary:
In conclusion, animals need to reproduce to maintain their population size, increase their numbers, and maintain the balance of nature. Reproduction is a natural process that ensures the survival and continuation of animal species. By reproducing, animals can sustain their population, expand their numbers, and fulfill their ecological roles in the ecosystem.

The correct life cycle is option 'D': Egg-caterpillar-pupa-butterfly.

Explanation:
Eggs are the first stage of a butterfly's life cycle. The female butterfly lays eggs on plants, typically on the underside of leaves. Each egg is tiny and usually round or oval in shape. The eggs are often laid in clusters.

Once the eggs hatch, caterpillars emerge. Caterpillars are the larval stage of a butterfly. They are small, worm-like creatures with a soft body and several pairs of legs. Caterpillars are voracious eaters and spend most of their time feeding on leaves and plants to grow.

After the caterpillar has grown to its full size, it forms a protective covering around itself called a pupa or chrysalis. Inside the pupa, the caterpillar undergoes a process called metamorphosis, where it transforms into an adult butterfly. This stage is also known as the transformation stage.

Finally, the adult butterfly emerges from the pupa. It takes some time for the butterfly's wings to expand and dry before it can fly. Once the wings are fully developed, the butterfly is ready to explore its surroundings and begin its adult life.

Key Points:
- Eggs are the first stage of a butterfly's life cycle.
- Caterpillars are the larval stage of a butterfly.
- Pupae or chrysalis is the protective covering formed by the caterpillar.
- The pupa undergoes metamorphosis, transforming into an adult butterfly.
- The adult butterfly emerges from the pupa and has fully developed wings.

The life cycle of a butterfly is a fascinating process of transformation and growth. It showcases the different stages a butterfly goes through before reaching adulthood. Each stage serves a specific purpose in the butterfly's development and contributes to its overall life cycle.

The eggs of the fish are called spawn.
Spawning is the process where fish release their eggs and sperm into the water, allowing fertilization to occur. The resulting eggs are commonly referred to as spawn. Here is a detailed explanation of the term spawn and its significance:
Definition of Spawn:
- Spawn refers to the eggs or reproductive cells of fish, amphibians, or other aquatic organisms.
- It is the initial stage of development for many aquatic species.
- The process of egg-laying or releasing eggs is known as spawning.
Key Points:
- Fish species have various spawning methods, including external and internal fertilization.
- External fertilization involves the release of eggs and sperm into the water, where fertilization occurs externally.
- Internal fertilization occurs when the female fish internally fertilizes the eggs with the sperm from the male fish before laying them.
Significance of Spawn:
- Spawn plays a crucial role in the reproduction and survival of fish populations.
- Fish eggs are usually laid in large quantities to increase the chances of survival for at least some of the offspring.
- These eggs serve as a food source for other aquatic organisms, contributing to the overall ecosystem balance.
- The eggs undergo various stages of development, eventually hatching into larvae, which then grow into juvenile fish.
Conclusion:
Spawn refers to the eggs of fish and other aquatic organisms. It is a crucial stage in the reproductive cycle of fish, allowing for fertilization and the continuation of the species. Understanding the concept of spawn is essential when studying fish and their life cycles.

Moulting

Yes the correct answer is B because lion, goat,and whale are all mammals

Explanation:

The larva of a butterfly is called a caterpillar. It is the first stage of the butterfly's life cycle and undergoes a complete metamorphosis to transform into an adult butterfly. Here is a detailed explanation of why the correct answer is option 'D' - Caterpillar.

Life Cycle of a Butterfly:
1. Egg: The life cycle of a butterfly starts with an egg. A female butterfly lays eggs on the leaves of plants. Each species of butterfly has its preferred host plants on which it lays eggs.
2. Caterpillar: Once the egg hatches, a larva emerges, which is commonly known as a caterpillar. Caterpillars have long segmented bodies with multiple pairs of legs. They are voracious eaters and feed on the leaves of the host plant.
3. Pupa: After the caterpillar reaches its full size, it forms a protective casing called a chrysalis or pupa. Inside the pupa, the caterpillar undergoes a process called metamorphosis, where it transforms into an adult butterfly.
4. Adult Butterfly: Finally, the adult butterfly emerges from the pupa. It takes a short while for the wings to expand and dry before the butterfly can fly. The adult butterfly then searches for a mate to reproduce and continue the life cycle.

Why is the answer 'D' - Caterpillar?
The larva of a butterfly is called a caterpillar because it has distinct characteristics that set it apart from other insects. Here are a few reasons why the answer is 'D' - Caterpillar:

1. Physical Appearance: Caterpillars have a unique body structure with a long, segmented body and multiple pairs of legs. They also have a distinct head with chewing mouthparts.
2. Feeding Behavior: Caterpillars are known for their voracious appetite and their primary purpose during this stage is to eat and grow. They consume large amounts of plant material, mainly leaves, to fuel their growth.
3. Distinct Life Stage: The caterpillar stage is a crucial part of the butterfly's life cycle. It is the stage where the insect undergoes most of its growth and development before entering the pupal stage.
4. Transformation: Caterpillars go through a remarkable transformation during metamorphosis. They completely change their body structure, including the formation of wings, which enables them to fly as adult butterflies.

In conclusion, the correct answer is option 'D' - Caterpillar because it is the larval stage of a butterfly, characterized by its physical appearance, feeding behavior, and role in the life cycle.

Mammals have constant body temperature.

Mammals are a group of animals that includes humans, dogs, cats, elephants, whales, and many others. One of the key characteristics of mammals is that they have a constant body temperature, also known as homeothermy. This means that their body temperature remains relatively stable regardless of the external temperature.

Reasons for constant body temperature:

There are several reasons why mammals have a constant body temperature:

1. Metabolism: Mammals have a high metabolic rate, which means that their bodies produce a lot of heat. This heat is generated through various metabolic processes such as digestion, respiration, and muscle activity. By maintaining a constant body temperature, mammals can ensure that their metabolic processes function optimally.

2. Enzyme activity: Enzymes, which are essential for various biochemical reactions in the body, work best at a specific temperature. By maintaining a constant body temperature, mammals can ensure that these enzymes work efficiently.

3. Physiological processes: Many physiological processes, such as the functioning of hormones, immune system, and nervous system, are temperature-dependent. By having a constant body temperature, mammals can ensure the proper functioning of these processes.

4. Adaptation: Mammals have evolved to regulate their body temperature through various mechanisms. For example, sweating and panting help to cool down the body when it gets too hot, while shivering and piloerection (raising hair) help to generate heat when it gets too cold.

Differences with other animals:

In contrast to mammals, other animals such as reptiles and amphibians have a changing body temperature, also known as poikilothermy. Their body temperature fluctuates with the temperature of their environment. For example, reptiles bask in the sun to raise their body temperature, and they seek shade or burrows to lower it.

Conclusion:

In conclusion, mammals have a constant body temperature due to their high metabolic rate, temperature-dependent physiological processes, and adaptation. This constant body temperature allows mammals to thrive in a wide range of environments and perform various biological functions efficiently.

Energy source at the larva stage

At the larva stage, energy is obtained from leaves.

Explanation

During the larva stage, which is the early stage of development for many organisms, energy is crucial for growth, development, and survival. The larva needs energy to carry out various physiological processes and to fuel its growth and development.

Obtaining energy from leaves

During this stage, the larva obtains energy from leaves by consuming them as their primary source of food. The larva feeds on the leaves of plants, extracting nutrients and energy from them.

Feeding on leaves

The larva typically has specialized mouthparts that are adapted for chewing and consuming plant material. By feeding on leaves, the larva obtains the necessary nutrients, including carbohydrates, proteins, and fats, which are all important sources of energy.

Metamorphosis and energy needs

The larva stage is a critical period in the life cycle of many organisms as it precedes metamorphosis. Metamorphosis is a process of transformation where the larva undergoes significant changes in its body structure and physiology to develop into its adult form. This transformation requires a considerable amount of energy.

Photosynthesis

While photosynthesis is a process that converts sunlight into chemical energy in plants, it is not the direct source of energy for the larva at this stage. Photosynthesis occurs in plants, where specialized structures called chloroplasts convert sunlight, water, and carbon dioxide into glucose, a form of energy-rich carbohydrate. The larva, however, does not possess the ability to carry out photosynthesis.

Other options

- Option A: Egg yolk is a potential energy source for the embryo within the egg, but it is not relevant to the larva stage.
- Option C: Photosynthesis, as explained earlier, is not directly applicable to the larva stage.
- Option D: Soil is not a source of energy for the larva stage. Soil may provide other essential nutrients, but not energy.

Therefore, the correct answer is option B, which states that at the larva stage, energy is obtained from leaves. The larva consumes leaves as its primary source of food to obtain the necessary energy for growth and development.

Mammals are the only animals that suckle their young.

Mammals are a class of vertebrate animals that possess mammary glands, which produce milk. The ability to produce milk is a defining characteristic of mammals and is crucial for the nourishment and growth of their young.

Here is a detailed explanation of why mammals are the only animals that suckle their young:

1. Mammary Glands:
Mammals have specialized glands called mammary glands, which are responsible for producing milk. These glands are present in both males and females, although they are usually functional only in females after pregnancy. The milk produced by mammary glands contains essential nutrients, antibodies, and growth factors that are vital for the survival and development of mammal offspring.

2. Nourishment:
Milk provides all the necessary nutrients, such as proteins, fats, carbohydrates, vitamins, and minerals, required for the growth and development of mammal young. It is a complete and balanced diet that meets the nutritional needs of the offspring during their early stages of life.

3. Lactation:
The process of providing milk to the young is called lactation. Mammal mothers nurse their young by allowing them to suckle milk directly from their mammary glands. The milk is usually delivered through specialized nipples or teats, which allow the offspring to latch on and draw milk.

4. Bonding and Care:
Suckling not only provides nourishment but also plays a crucial role in bonding between the mother and her offspring. It helps create a strong emotional attachment and fosters a sense of security for the young ones. The act of suckling also allows the mother to monitor the health and well-being of her offspring closely.

5. Gradual Weaning:
As the young mammals grow and develop, they gradually transition from a milk-only diet to solid food. This process is known as weaning. The timing and method of weaning vary among different mammal species, but it typically involves introducing solid foods while continuing to provide milk until the young ones can sustain themselves entirely on solid food.

In conclusion, mammals are the only animals that suckle their young due to the presence of specialized mammary glands that produce milk. This unique characteristic allows mammal offspring to receive vital nutrients, establish a bond with their mother, and ensure their healthy growth and development.

Yes, because bats give birth to young ones. They don't lay eggs

Correct answer is 'C' because the following picture is a pupa of caterpillar and after some time the pupa will turn into a butterfly

Answer:

In order to determine which set consists of only mammals, we need to understand what mammals are and identify the animals in each set. Mammals are a group of animals that have certain characteristics:

1. Warm-blooded: Mammals have a constant body temperature, which means their bodies do not change temperature with the environment.

2. Have fur or hair: Mammals have some form of fur or hair on their bodies, even if it is very fine or sparse.

3. Breathe air: Mammals have lungs and breathe in oxygen from the air.

4. Bear live young: Mammals give birth to live young that are nourished with milk produced by the mother.

Now let's analyze each set of animals to identify the mammals:

a) Lion, hen, and human beings
- Lion: Lions are mammals as they have fur, are warm-blooded, breathe air, and give birth to live young.
- Hen: Hens are birds, not mammals, as they have feathers, lay eggs, and have a beak.
- Human beings: Humans are mammals as they have fur (hair), are warm-blooded, breathe air, and give birth to live young.

From set a), we can see that only one out of the three animals (lion) is a mammal. Therefore, this set does not consist of only mammals.

c) Tigers, sheep, and crocodiles
- Tigers: Tigers are mammals as they have fur, are warm-blooded, breathe air, and give birth to live young.
- Sheep: Sheep are mammals as they have fur, are warm-blooded, breathe air, and give birth to live young.
- Crocodiles: Crocodiles are reptiles, not mammals, as they have scales, lay eggs, and have a snout.

From set c), we can see that two out of the three animals (tigers and sheep) are mammals. Therefore, this set does not consist of only mammals.

d) Birds, butterflies, and frogs
- Birds: Birds are not mammals as they have feathers, lay eggs, and have a beak.
- Butterflies: Butterflies are insects, not mammals, as they have six legs, wings, and a proboscis.
- Frogs: Frogs are amphibians, not mammals, as they have moist skin, lay eggs in water, and undergo metamorphosis.

From set d), we can see that none of the animals are mammals. Therefore, this set does not consist of only mammals.

b) Lions, goats, and whales
- Lions: Lions are mammals as they have fur, are warm-blooded, breathe air, and give birth to live young.
- Goats: Goats are mammals as they have fur, are warm-blooded, breathe air, and give birth to live young.
- Whales: Whales are mammals as they have fur (blubber), are warm-blooded, breathe air, and give birth to live young.

From set b), we can see that all of the animals (lions, goats, and whales) are mammals. Therefore, this set consists of only mammals.

Therefore, the correct answer is option B (Lions, goats, and whales).

Stored Food in Egg Yolk

The egg yolk is the part of the egg that contains all the nutrients required for the growth and development of the embryo. Here are the details on how stored food in egg yolk gives energy to the embryo:

• Rich in Nutrients: The egg yolk is rich in nutrients like protein, fat, vitamins, and minerals that are essential for the growth and development of the embryo.

• Source of Energy: The stored food in the egg yolk serves as a source of energy for the developing embryo. The yolk contains a high amount of lipids, which are broken down to release energy.

• Sustains Life: The egg yolk provides the necessary nutrients and energy to the developing embryo, allowing it to sustain life until it hatches.

• Nutrient Absorption: The embryo absorbs the nutrients from the egg yolk through the yolk sac, which is attached to the embryo's digestive system.

• Essential for Growth: The stored food in the egg yolk is essential for the growth and development of the embryo. Without it, the embryo cannot develop properly, and its chances of survival decrease.

In conclusion, the egg yolk contains stored food that serves as a source of energy for the developing embryo. It is rich in nutrients and is essential for the growth and development of the embryo.

Most frogs deposit their eggs in quiet water

as clumps, surface films, strings, or individual

eggs. The eggs may be freely suspended in

the water or attached to sticks or submerged

vegetation. so it is an egg laying animal

Energy Source at the Egg Stage:
- Egg Yolk: The main source of energy at the egg stage is the egg yolk present in the egg. The yolk contains various nutrients, including proteins, fats, and vitamins, which provide the necessary energy for the developing embryo during this stage.
- Leaves of the Plant: While leaves are an essential part of a plant's life cycle, they do not directly provide energy to the egg stage. Photosynthesis, which occurs in the leaves, is crucial for the production of energy in the form of carbohydrates. However, at the egg stage, the developing embryo relies on the energy stored in the egg yolk rather than obtaining it from the leaves.
- Killing Other Insects: Insects generally do not obtain energy by killing other insects during the egg stage. Predatory behavior and the consumption of other insects usually occur at later stages of the insect's life cycle, such as during the larval or adult stages.
- Photosynthesis: Photosynthesis is the process by which plants convert sunlight, water, and carbon dioxide into energy-rich carbohydrates. While photosynthesis is vital for the growth and development of plants, it does not directly provide energy to the egg stage of insects. Insects rely on other sources of energy, such as the egg yolk, to fuel their development during this stage.
Therefore, the correct answer is B: Egg yolk present in the egg, as it is the primary source of energy for the developing embryo at the egg stage.