SECTION – A (Very short answer questions)
1. What is meant by tautonymy? Give two examples.
Answer:
Tautonymy refers to the practice of giving an organism a scientific name where both the genus and species are identical. This occurs in certain species, often in plants, where the genus name is repeated as the species name.
Examples:
- Bison bison (American bison)
- Gorilla gorilla (Western gorilla)
Explanation: Tautonymy is used when a species name and genus name are the same, typically in a taxonomic context. This naming system helps avoid confusion when referencing certain organisms. It’s a rare but interesting feature in biological classification.
2. What is monaxial heteropolar symmetry? Name the group of animals in which it is the principal symmetry.
Answer:
Monaxial heteropolar symmetry refers to a type of symmetry where an organism’s body is arranged along a single axis with distinct polar ends (e.g., anterior and posterior). The body shape is elongated, and it has asymmetry along the central axis.
Group of animals:
- Example: Nematodes (roundworms)
Explanation: In animals with monaxial heteropolar symmetry, the body structure is typically tubular, with a clear differentiation of ends (anterior and posterior), leading to a well-defined front and back. Nematodes, which exhibit this symmetry, are examples of animals with this type of body structure.
3. Name the animals that exhibited a ‘tube-within-a-tube’ organisation for the first time. Name their body cavity.
Answer:
The “tube-within-a-tube” organization was first exhibited by annelids (segmented worms).
Body cavity:
- Coelom (a fluid-filled body cavity)
Explanation: The “tube-within-a-tube” organization refers to an arrangement where the digestive system forms a tube running through the body, with another tube (the body wall) surrounding it. Annelids were among the first to show this feature, signifying a more advanced body organization compared to earlier organisms.
4. Distinguish between holocrine and apocrine glands.
Answer:
- Holocrine glands: These glands secrete their products by the entire cell disintegrating, releasing the secretion and the cell debris.
Example: Sebaceous glands in skin. - Apocrine glands: These glands release their secretion by pinching off a part of the cell, allowing it to regenerate.
Example: Mammary glands.
Explanation: The key difference lies in the mode of secretion. Holocrine glands release whole cells, whereas apocrine glands only lose part of the cell during secretion, resulting in different structural adaptations.
5. Distinguish between amphids and phasmids.
Answer:
- Amphids: Sensory organs found in nematodes that detect chemical signals or environmental cues, usually located at the anterior end of the body.
- Phasmids: Sensory structures found in some nematodes, similar to amphids, but located at the posterior end of the body.
Explanation: Both are sensory organs but differ in location and possibly function. Amphids are more common and serve as sensory organs for environmental interaction, whereas phasmids are often involved in detecting chemical signals in the environment and are located on the posterior end.
6. How do you justify the statement – “Heart in fishes is a branchial heart”?
Answer:
In fishes, the heart pumps blood through the gills before it is circulated to the rest of the body, meaning the heart is directly involved in supplying oxygenated blood to the gills. This makes it a “branchial heart” because it primarily serves the branchial (gill) circulation.
Explanation: Fishes have a two-chambered heart, and the heart pumps deoxygenated blood to the gills, where it is oxygenated before being sent to the rest of the body. Hence, the heart is often referred to as a branchial heart.
7. Draw a labelled diagram of T.S of flagellum.
Answer:
Since I can’t draw, I can describe the structure in detail:
A transverse section (T.S.) of a flagellum shows a central core known as the axoneme, consisting of a “9+2” arrangement of microtubules (nine outer pairs and two central microtubules). The flagellum is surrounded by a plasma membrane. The basal body anchors the flagellum to the cell.
Explanation: The flagellum’s structure is designed for movement, and the microtubules slide against each other to allow it to move in a whip-like fashion. The axoneme is the core structural component essential for motility.
8. What are dynein arms? What is their significance?
Answer:
Dynein arms are motor protein complexes that extend from the outer microtubule doublets of the axoneme in flagella and cilia. They play a crucial role in the movement of these structures by using ATP energy to slide microtubules past one another.
Significance: Dynein arms allow for the bending and movement of cilia and flagella, which is vital for cellular motility, such as sperm movement or the clearing of mucus in the respiratory tract.
9. What do you mean by parasitic castration? Give one example.
Answer:
Parasitic castration refers to the process where a parasitic organism reduces or inhibits the reproductive ability of its host. This is typically done to divert the host’s resources for the parasite’s own growth or reproduction.
Example:
- Sacculina (a parasitic barnacle) castrates crabs by manipulating their reproductive system.
Explanation: The parasite invades the host, altering its hormonal balance and effectively preventing reproduction, ensuring the host’s energy is used for the parasite’s benefit.
10. Explain the difference between the ‘niche’ of an organism and its ‘habitat’.
Answer:
- Niche: Refers to the role or function of an organism within its environment, including its interactions with other species, its food sources, and its behavior.
- Habitat: Refers to the physical environment where an organism lives, such as a forest, ocean, or desert.
Explanation: The niche is about an organism’s lifestyle, ecological role, and interactions, whereas the habitat is the physical location it occupies. The niche describes “how” an organism lives, while the habitat describes “where” it lives.
These answers cover key biological concepts, focusing on clarity and concise explanation suitable for understanding and memorizing the topics.
Here are the answers to the six questions in 20 lines each:
SECTION – B (Short answer questions)
11. What is ‘Evil Quartet’?
Answer:
The term “Evil Quartet” refers to a set of four main causes responsible for the rapid extinction of species, particularly in the context of biodiversity loss. These four factors are:
- Habitat destruction – The loss or alteration of natural habitats due to human activities like deforestation, urbanization, and agriculture.
- Over-exploitation – Overhunting, fishing, or harvesting of species beyond their ability to regenerate, leading to population declines.
- Introduction of alien species – Invasive species that are introduced into new ecosystems, often outcompeting or preying on native species.
- Climate change – Global changes in temperature, weather patterns, and sea levels that disrupt ecosystems and threaten species’ survival.
These four factors are often interrelated, with one exacerbating the effects of the others, leading to accelerated extinction rates. The “Evil Quartet” highlights the urgent need for conservation efforts to tackle these challenges and protect biodiversity from irreversible losses. The term was coined by famous biologist Stuart Pimm in the 1980s to emphasize the critical threats faced by wildlife.
12. Describe the structure of a multipolar neuron with the help of a diagram.
Answer:
A multipolar neuron is a type of nerve cell that has multiple processes (extensions) extending from its cell body. It is the most common type of neuron found in the human body, especially in the central nervous system. The main components are:
- Cell body (Soma): Contains the nucleus and other organelles. It is the metabolic center of the neuron.
- Dendrites: Short, branched extensions that receive electrical signals from other neurons. Multipolar neurons typically have many dendrites.
- Axon: A long, slender projection that transmits electrical impulses away from the cell body to other neurons, muscles, or glands. It is often covered by myelin, which speeds up the transmission.
- Axon Terminals: At the end of the axon, these release neurotransmitters to communicate with other cells.
- Myelin sheath: Insulates the axon, speeding up signal transmission.
Diagram:
Dendrites
|
|
___|___
| |
| Soma |
|_______|
|
|
Axon --> Axon Terminals
Explanation: The multipolar neuron is crucial for transmitting signals in the nervous system. Its structure allows it to receive signals from many other neurons and send out signals over long distances. Multipolar neurons are involved in motor functions and higher-level processes like thinking and learning.
13. What are the salient features of the echinoids?
Answer:
Echinoids, commonly known as sea urchins, belong to the class Echinoidea in the phylum Echinodermata. Their salient features include:
- Radial Symmetry: Adult echinoids exhibit pentaradial symmetry, meaning their body parts are arranged in five equal segments around a central axis.
- Endoskeleton: The internal skeleton, or test, is made up of calcareous plates that form a rigid, spiny outer covering.
- Spines: Echinoids have sharp, movable spines that provide protection and help in movement.
- Tube Feet: Located on the underside, these tube feet are used for locomotion and feeding. They operate using water vascular systems.
- Aristotle’s Lantern: A unique mouth structure composed of five calcareous teeth used for feeding, particularly in grazing species.
- Respiration: They respire through tube feet and specialized structures called papulae.
- Habitat: Echinoids are found in marine environments, particularly on the ocean floor in various depths.
- Reproduction: Most echinoids are dioecious, with external fertilization during spawning.
Echinoids play an important role in marine ecosystems, primarily as herbivores that graze on algae, contributing to maintaining the balance of coral reef ecosystems.
14. Compare and contrast cartilaginous and bony fishes.
Answer:
Cartilaginous Fishes (Class Chondrichthyes):
- Skeleton: Made of cartilage, which is lighter but less rigid than bone.
- Examples: Sharks, rays, skates.
- Scales: Possess placoid scales (like teeth), which provide protection and reduce friction.
- Respiratory System: Have gills that are not covered by operculum (gill covers).
- Reproduction: Internal fertilization is common; some species are oviparous, ovoviviparous, or viviparous.
- Buoyancy: Lack a swim bladder and rely on large, oil-filled liver for buoyancy.
Bony Fishes (Class Osteichthyes):
- Skeleton: Made of bones, which are harder and stronger.
- Examples: Salmon, goldfish, tuna.
- Scales: Have cycloid or ctenoid scales, which are smooth and flexible.
- Respiratory System: Have gills covered by an operculum, which helps in efficient water flow.
- Reproduction: Mostly external fertilization, with many species being oviparous.
- Buoyancy: Have a swim bladder to maintain buoyancy in water.
Comparison: Cartilaginous fishes have cartilaginous skeletons and lack a swim bladder, while bony fishes have bones and a swim bladder. Both groups have gills for respiration, but bony fishes have an operculum to cover their gills.
15. Describe the process of transverse binary fission in Paramecium.
Answer:
Transverse binary fission is a method of asexual reproduction in Paramecium, a type of single-celled organism. The process involves the following steps:
- Pre-fission Preparation: The macronucleus and micronucleus undergo replication. The micronucleus forms a copy of itself (this is essential for genetic material distribution).
- Cell Elongation: The Paramecium cell elongates as the internal structures start to divide.
- Nuclear Division: The macronucleus divides by amitosis (simple division), while the micronucleus divides by mitosis.
- Division of Cytoplasm: The cytoplasm starts dividing along the cell’s length. A groove, known as the cleavage furrow, begins to form across the body of the cell.
- Separation: The cleavage furrow deepens until the cell is divided into two equal halves, each with its own set of organelles and nuclei.
- Post-fission: Each daughter cell is a genetically identical copy of the parent.
Transverse binary fission allows Paramecium to rapidly reproduce under favorable conditions, helping the species increase its population.
16. “Prevention is better than cure”. Justify with regard to TDA abuse.
Answer:
The statement “Prevention is better than cure” is especially true when it comes to the abuse of TDA (Tobacco, Drugs, and Alcohol). Here’s why:
- Health Risks: The use of tobacco, drugs, and alcohol can lead to chronic diseases like cancer, liver disease, heart problems, and mental health disorders. Once these conditions are established, they are difficult and expensive to treat.
- Addiction and Dependency: TDA abuse often leads to addiction, which is harder to treat and can lead to long-term physical and psychological dependence.
- Social and Economic Costs: Treating the consequences of substance abuse is expensive and puts a significant burden on healthcare systems. Preventing abuse helps save resources and reduce societal costs related to crime and healthcare.
- Quality of Life: Prevention helps individuals lead healthier, more productive lives. It is easier to avoid the consequences of TDA abuse through education and lifestyle changes than to attempt to rehabilitate afterward.
- Health Education: Prevention programs that promote awareness and provide coping mechanisms reduce the incidence of abuse, improving public health outcomes.
By focusing on education, awareness, and early intervention, society can avoid the devastating long-term effects of TDA abuse, making prevention the better approach.
17. Draw a neat, labeled diagram of the mouthparts of cockroach.
Answer:
Since I can’t draw, I can describe the mouthparts of a cockroach:
The cockroach’s mouthparts are complex and adapted for biting and chewing:
- Labrum: The upper lip that covers the mouth opening.
- Mandibles: Strong, chitinous structures used for cutting and grinding food.
- Maxillae: Pair of appendages used for manipulating food and sensing its quality.
- Labium: The lower lip that holds the food and helps in tasting.
- Palps (Maxillary and Labial Palps): Sensory structures that help in tasting and handling food.
The diagram would show the arrangement of these parts surrounding the mouth opening, highlighting their roles in feeding.
18. Discuss the causes and effects of “Global Warming”. What measures need to be taken to control “Global Warming”?
Answer:
Causes of Global Warming:
- Greenhouse Gas Emissions: The burning of fossil fuels like coal, oil, and natural gas releases carbon dioxide (CO2) and methane (CH4), which trap heat in the Earth’s atmosphere.
- Deforestation: Trees absorb CO2; cutting them down reduces the planet’s ability to remove greenhouse gases.
- Industrial and Agricultural Practices: Agricultural practices like livestock farming emit methane, while industrial processes release various pollutants contributing to global warming.
- Waste and Pollution: Landfills release methane, and air pollution from cars and factories contributes to the warming effect.
Effects of Global Warming:
- Rising Temperatures: Increased global temperatures lead to heatwaves, changing weather patterns, and extreme climates.
- Melting Ice Caps: The Arctic and Antarctic ice caps are melting, causing sea levels to rise, which threatens coastal habitats.
- Disrupted Ecosystems: Changing temperatures and weather patterns disrupt habitats, leading to loss of biodiversity.
- Health Risks: Warmer climates can cause heat-related illnesses, while the spread of diseases like malaria and dengue increases.
Measures to Control Global Warming:
- Reduce Greenhouse Gas Emissions: Transition to renewable energy sources like solar, wind, and hydroelectric power.
- Reforestation: Planting trees to absorb CO2 and restore ecosystems.
- Energy Efficiency: Improving energy efficiency in industries, homes, and transportation systems.
- Carbon Sequestration: Techniques to capture and store CO2 emissions.
- International Cooperation: Global agreements like the Paris Agreement can promote collective action to mitigate climate change.
SECTION – C (Long answer questions)
19. Describe the life cycle of Plasmodium vivax in the mosquito with the help of a neat, labeled diagram.
Answer: The life cycle of Plasmodium vivax, the protozoan responsible for malaria, involves both human hosts and female Anopheles mosquitoes. The cycle consists of two main phases: the asexual cycle in humans and the sexual cycle in mosquitoes.
1. Infection of Humans:
- When an infected female Anopheles mosquito bites a human, it injects sporozoites (the infective form of Plasmodium) into the bloodstream.
- These sporozoites travel to the liver, where they invade liver cells and undergo asexual reproduction, forming merozoites.
2. Asexual Reproduction in Liver:
- Inside the liver, sporozoites mature into liver cells and undergo schizogony (asexual division), forming large numbers of merozoites.
- These merozoites are released into the bloodstream, where they invade red blood cells.
3. Asexual Reproduction in Red Blood Cells:
- Inside red blood cells, the merozoites continue to divide, producing more merozoites in a process called trophozoite formation.
- The infected red blood cells rupture, releasing new merozoites that go on to infect more red blood cells.
- This cycle of infection and destruction of red blood cells leads to the symptoms of malaria, such as fever and chills.
4. Formation of Gametocytes:
- Some of the merozoites in the red blood cells differentiate into gametocytes (sexual forms of the parasite), which are either male or female.
- These gametocytes circulate in the human blood, ready to be ingested by a mosquito.
5. Sexual Cycle in the Mosquito:
- When a mosquito bites an infected human, it ingests the gametocytes along with the blood meal.
- Inside the mosquito’s stomach, the gametocytes mature into male and female gametes.
- Fertilization occurs when the male and female gametes unite, forming a zygote.
6. Oocyst Formation:
- The zygote transforms into an ookinete, which burrows into the mosquito’s gut wall and forms an oocyst.
- Inside the oocyst, sporogony (sexual reproduction) occurs, leading to the formation of sporozoites.
- These sporozoites migrate to the mosquito’s salivary glands, ready to be transmitted to another human host during the next bite.
7. Transmission to Humans:
- When the infected mosquito bites a human, the sporozoites in the mosquito’s salivary glands are injected into the human, continuing the cycle.
Summary of the Life Cycle in Mosquito:
- Sporozoites are injected into the human blood during a mosquito bite.
- Sporozoites migrate to the liver, where they form merozoites.
- Merozoites infect red blood cells, leading to the release of more merozoites and the formation of gametocytes.
- Mosquitoes ingest gametocytes, which undergo fertilization and produce sporozoites.
- These sporozoites travel to the mosquito’s salivary glands, completing the cycle.
20. Describe the blood circulatory system of Periplaneta and draw a neat labelled diagram of it.
Answer: The blood circulatory system of the cockroach (Periplaneta americana) is open and is primarily responsible for the distribution of nutrients, gases, and hormones to the body. However, it does not have veins and arteries as in higher animals; instead, the blood (hemolymph) flows freely within body cavities.
Key Features of Cockroach Circulatory System:
- Heart:
- The cockroach has a dorsal heart, which is a long, tube-like structure running along the back of the thorax and abdomen.
- The heart consists of several chambers with ostia (small openings) that allow the entry of hemolymph from the body cavity.
- Hemolymph:
- The cockroach’s blood is called hemolymph, which is a pale, colorless fluid containing nutrients, hormones, and waste products.
- Hemolymph circulates through the hemocoel (body cavity), bathing the internal organs and tissues.
- Hemocoel:
- The hemocoel is the large body cavity that contains all the internal organs. It functions as the primary space for the circulation of hemolymph.
- Heart Chambers and Ostia:
- The heart has four chambers, and each chamber has a pair of ostia (pores). These ostia are controlled by valves that regulate the entry of hemolymph.
- The chambers are sequentially numbered, starting from the posterior end (abdomen) and moving towards the anterior end (thorax).
- Circulatory Path:
- The heart pumps the hemolymph from the posterior end of the body towards the anterior end. As the heart contracts, hemolymph enters the heart from the body cavity via the ostia.
- The hemolymph then moves forward, reaching the head and thorax before returning to the body cavity.
- Open Circulatory System:
- Unlike closed circulatory systems (in humans), the cockroach has an open system where the hemolymph freely flows through the body cavity and directly bathes the organs.
- There is no distinction between blood vessels and body cavities.
- Aorta:
- From the heart, a major artery, the aorta, extends forward to supply hemolymph to the head and thorax. It has no branching and serves as a conduit for hemolymph.
- Blood Flow:
- As the hemolymph circulates, it moves through the tissues, providing nutrients and removing waste products.
- The flow of hemolymph is controlled by the heart’s rhythmic contractions and is aided by body movements, such as the cockroach’s walking or flying.
Diagram of the Cockroach Circulatory System:
_________
| | ← Head
| Heart |
|_________|
|
________________
| | ← Thorax
| Hemocoel |
|________________|
|
________________
| | ← Abdomen
| Hemocoel |
|________________|
|
________________
| |
| Heart (4 Chambers) |
|________________|
Explanation:
- The diagram shows the cockroach’s dorsal heart, located on the back of the body.
- The hemolymph circulates through the hemocoel (body cavity), bathing the internal organs.
- The ostia (openings in the heart) allow the hemolymph to enter the heart during its relaxation phase.
- The flow of hemolymph is directed by the heart’s pumping action, moving from the posterior abdomen to the anterior end.
21. Describe different types of food chains that exist in an Ecosystem.
Answer: A food chain represents the flow of energy and nutrients from one organism to another in an ecosystem. It shows how energy is passed through various trophic levels, from primary producers to top predators. There are several types of food chains based on the organisms involved:
1. Grazing Food Chain:
- Primary Producers: These are typically plants or algae that use sunlight to produce their own food through photosynthesis.
- Primary Consumers (Herbivores): These organisms feed on primary producers. Example: Grasshoppers feeding on grass.
- Secondary Consumers (Carnivores): These are animals that feed on herbivores. Example: Frogs feeding on grasshoppers.
- Tertiary Consumers: Top predators that feed on secondary consumers. Example: Snakes feeding on frogs.
- Decomposers: Organisms like bacteria and fungi that break down dead organisms, returning nutrients to the soil.
Example Food Chain:
Grass → Grasshopper → Frog → Snake → Decomposers.
2. Detritus Food Chain:
- Primary Producers: Detritus (dead organic matter) and decomposing organisms such as fallen leaves.
- Detritivores: Organisms like earthworms, fungi, and beetles that feed on detritus.
- Secondary Consumers: Small carnivores that feed on detritivores.
- Tertiary Consumers: Larger carnivores that feed on secondary consumers.
- Decomposers: Break down organic material and recycle nutrients.
Example Food Chain:
Dead leaves → Earthworms → Birds → Larger Carnivores.
3. Parasite-Host Food Chain:
- This type of food chain involves parasitism, where one organism (the parasite) benefits at the expense of the other (the host).
- Primary Producer: Can include plants or algae.
- Parasites: Organisms that feed on the host, such as ticks, lice, or tapeworms.
- Hosts: Organisms that are parasitized.
- This type of food chain is typically shorter and involves energy transfer through parasitic interactions.
Example Food Chain:
Grass → Cow → Tapeworm → Decomposers.
4. Marine Food Chain:
- In marine ecosystems, the food chain is similar but includes marine plants and animals.
- Primary Producers: Phytoplankton and seaweeds.
- Primary Consumers: Zooplankton that feed on phytoplankton.
- Secondary Consumers: Small fish that feed on zooplankton.
- Tertiary Consumers: Larger fish or marine mammals that prey on smaller fish.
- Top Predators: Sharks, orcas, and other apex predators.
Example Food Chain:
Phytoplankton → Zooplankton → Small Fish → Large Fish → Shark.
5. Food Web:
- A food web consists of several interlinked food chains within an ecosystem, showing how multiple organisms at different trophic levels are interconnected. It provides a more accurate representation of energy flow in ecosystems, as most organisms eat multiple species and are eaten by others.
Example: A deer may eat grasses, but also browse on shrubs. A fox may eat rabbits, but could also prey on birds.
Importance of Food Chains:
- They help to demonstrate energy flow in an ecosystem.
- They show the relationship between different organisms at various trophic levels.
- They highlight the interconnectedness of species and the balance of ecosystems.
Conclusion:
Food chains, whether grazing, detritus-based, or parasite-host, form the foundation of ecosystem structure and function. The complexity of food webs reflects the diverse interactions between organisms, ensuring the stability and functioning of ecosystems.