CBSE Class 9 Science Diversity in Living Organisms Assignment Set 01

 

Question : How do gymnosperms and angiosperms differ from each other?

Answer :

 

 

Question : How do poriferan animals differ from coelenterate animals?

Answer : 

Diversity in Living Organisms

Q 1 Name the branch of the biology that deals with the classification.
Answer: Taxonomy is the branch of biology that deals with the identification, nomenclature, and classification of organisms.
In simple words: Taxonomy is the science of grouping and naming living things.

Exam Tip: Remember that taxonomy involves both classification and scientific naming.

Q 2 Who was the first to propose the two-kingdom system of classification?
Answer: Carolus Linnaeus was the first to propose the two-kingdom system of classification, dividing all living organisms into Kingdom Plantae and Kingdom Animalia.
In simple words: Linnaeus created the system that divided life into plants and animals.

Exam Tip: Associate Carolus Linnaeus directly with the two-kingdom classification system.

Q 3 Who proposed three-kingdom classification?
Answer: Ernst Haeckel proposed the three-kingdom classification system, adding Kingdom Protista to the existing plant and animal kingdoms.
In simple words: Haeckel added a third kingdom for single-celled organisms.

Exam Tip: Note that Haeckel introduced Protista to accommodate microorganisms.

Q 4 What is meant by triploblastic?
Answer: Triploblastic animals are those in which the developing embryo has three primary germ layers: ectoderm, mesoderm, and endoderm.
In simple words: Triploblastic means having three layers of cells in the embryo.

Exam Tip: Always list all three layers (ectoderm, mesoderm, endoderm) when defining triploblastic.

Q 5 What is haemocoel?
Answer: A haemocoel is a blood-filled cavity or body cavity found in arthropods and molluscs where the blood (haemolymph) bathes the organs directly instead of being enclosed in vessels.
In simple words: It is an open body space filled with blood in certain animals.

Exam Tip: Haemocoel is characteristic of animals with an open circulatory system.

Q 6 Name the person who has given the five-kingdom classification.
Answer: R.H. Whittaker proposed the five-kingdom classification system in 1969.
In simple words: Whittaker classified all life into five distinct kingdoms.

Exam Tip: Memorize the five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia.

Q 7 Which is the largest phylum of animal kingdom?
Answer: Arthropoda is the largest phylum in the animal kingdom, comprising insects, arachnids, and crustaceans.
In simple words: Arthropoda contains the highest number of animal species, mostly insects.

Exam Tip: Insects form the vast majority of species within Phylum Arthropoda.

Q 8 What is the function of canal system in sponges?
Answer: The canal system in sponges helps in water transport, bringing in food and oxygen, and removing waste products and carbon dioxide.
In simple words: Water flows through canals to provide food and oxygen while taking away wastes.

Q 9 What are Gymnosperms?
Answer: Gymnosperms are seed-bearing plants in which the seeds are naked, meaning they are not enclosed within an ovary or fruit.
In simple words: Gymnosperms are plants with naked seeds, such as pines and firs.

Exam Tip: The key term to include in your definition is naked seeds.

Q 10 What is the purpose of classification?
Answer: The main purposes of classification are:
1. To make the study of a vast variety of living organisms easy and systematic.
2. To understand the evolutionary relationships between different groups of organisms.
3. To identify and assign correct positions to newly discovered organisms.
In simple words: Classification organizes living things so they are easier to study and understand.

Exam Tip: Highlight identification, ease of study, and evolutionary relationships.

Q 11 What do you mean by evolution?
Answer: Evolution is the gradual and continuous process by which complex life forms have developed from simpler ancestral forms over millions of years through genetic changes and adaptation.
In simple words: Evolution is how living things change and become more complex over long periods.

Exam Tip: Use the words gradual, ancestral forms, and complexity in your answer.

Q 12 What are the bases due to which plants and animals are classified as different categories?
Answer: Plants and animals are classified differently based on:
1. Mode of nutrition (autotrophic in plants vs. heterotrophic in animals).
2. Presence or absence of cell walls (plants possess rigid cellulose cell walls, whereas animal cells lack cell walls).
3. Locomotion (most plants are stationary, while most animals can move freely).
In simple words: Plants make their own food and have cell walls, while animals eat other organisms and can move around.

Q 13 What are the four main characteristics of chordates?
Answer: The four defining characteristics of chordates are:
1. Presence of a notochord at some stage of life.
2. A dorsal tubular nerve cord.
3. Paired pharyngeal gill slits.
4. A post-anal tail.
In simple words: All chordates have a stiff rod-like notochord, a nerve cord, gill slits, and a tail at some point.

Exam Tip: Learn all four features precisely as they define Phylum Chordata.

Q 14 Draw the hierarchy of the classification?
Answer: The taxonomic hierarchy flows from the broadest category to the most specific species:
Kingdom 
\(\downarrow\)
Phylum (for animals) / Division (for plants)
\(\downarrow\)
Class
\(\downarrow\)
Order
\(\downarrow\)
Family
\(\downarrow\)
Genus
\(\downarrow\)
Species
In simple words: Classification goes from very large groups down to single species.

Exam Tip: Remember the mnemonic: King Philip Came Over For Good Soup.

Q 15 Give the names of different groups of Plant Kingdom.
Answer: The Plant Kingdom is broadly divided into:
1. Thallophyta (Algae)
2. Bryophyta (Mosses)
3. Pteridophyta (Ferns)
4. Gymnosperms (Naked-seeded plants)
5. Angiosperms (Flowering plants)
In simple words: Plants are divided into five main groups ranging from simple algae to flowering plants.

Q 16 Will advanced organisms be the same as complex organisms? Why?
Answer: No, advanced organisms are not necessarily the same as complex organisms. "Advanced" refers to organisms that have evolved more recently and adapted well to their environments, whereas "complex" refers to the degree of cellular and anatomical differentiation. A relatively simple organism can be highly successful and advanced without having a highly complex body design.
In simple words: Newer or well-adapted organisms are not always structurally the most complex.

Exam Tip: Distinguish between evolutionary advancement (adaptation over time) and structural complexity.

Q 17 Give one example each of Hemichordata, Urochordata, Cephalochordata and Vertebrata.
Answer: 1. Hemichordata: Balanoglossus (Acorn worm)
2. Urochordata: Ascidia (Sea squirt)
3. Cephalochordata: Amphioxus (Lancelet)
4. Vertebrata: Homo sapiens (Human) or Panthera leo (Lion)
In simple words: Examples include acorn worms for hemichordates, sea squirts for urochordates, lancelets for cephalochordates, and humans for vertebrates.

Exam Tip: Practice these standard representative examples for protochordates.

Q 18 Pick the odd one out and justify your choice by giving reasons.
i) Coelenterates, Echinoderms, Vertebrates, Molluscs
ii) Chicken, Bat, Ostrich, Penguin
Answer: i) Vertebrates. Reason: All others are invertebrates, whereas vertebrates possess a vertebral column.
ii) Bat. Reason: Bat is a mammal that gives birth to live young and has mammary glands, whereas chicken, ostrich, and penguin are birds that lay eggs.
In simple words: Vertebrates stands out because it has a backbone, and bat stands out because it is a mammal among birds.

Exam Tip: Clearly state both the odd element and the scientific reason for your choice.

Q 19 Pick the odd one out and justify your choice by giving reasons.
i) Riccia, Marsilea, Marchantia, Funaria
ii) Crocodile, Salamander, Sparow, Bat
Answer: i) Marsilea. Reason: Marsilea is a pteridophyte (vascular cryptogam), whereas Riccia, Marchantia, and Funaria are bryophytes (non-vascular).
ii) Bat. Reason: Bat is a warm-blooded mammal, whereas crocodiles (reptile), salamanders (amphibian), and sparrows (bird) belong to different vertebrate classes (and sparrows/crocodiles lay eggs).
In simple words: Marsilea is a vascular plant unlike the other mosses/liverworts, and bat is a mammal among egg-laying vertebrates.

Q 20 To which major group do the following belong?
i) Bat
ii) Cycas
iii) Plasmodium
iv) Mosquito
Answer: i) Bat: Class Mammalia (Phylum Chordata)
ii) Cycas: Division Gymnospermae (Plant Kingdom)
iii) Plasmodium: Kingdom Protista (Protozoa)
iv) Mosquito: Phylum Arthropoda (Class Insecta)
In simple words: Bat is a mammal, Cycas is a gymnosperm, Plasmodium is a protist, and mosquito is an arthropod.

Q 21 Give two points of difference between Chondrichthyes and Osteichthyes.
Answer: 1. Endoskeleton: Chondrichthyes have an endoskeleton made entirely of cartilage, whereas Osteichthyes have a bony endoskeleton.
2. Gill Covers: Chondrichthyes lack an operculum (gill cover) over their gills, whereas Osteichthyes possess an operculum covering their gills.
In simple words: Cartilaginous fishes have soft skeletons and no gill covers, while bony fishes have hard bones and gill covers.

Exam Tip: Cartilage vs. bone and presence/absence of operculum are the two most reliable differences.

Q 22 Differentiate between Poriferans and Coelenterates.
Answer: 1. Organization: Poriferans have cellular level of body organization, while coelenterates have tissue level of organization.
2. Body Opening: Poriferans have numerous pores (ostia) and a canal system with a central cavity (spongocoel), whereas coelenterates have a single gastrovascular cavity with one opening for mouth and anus.
3. Symmetry: Poriferans are mostly asymmetrical, whereas coelenterates exhibit radial symmetry.
In simple words: Sponges have simple cell aggregates with pores, while coelenterates have tissues and a central body cavity with tentacles.

Exam Tip: Focus on organization level, symmetry, and body openings.

Q 23 Give two examples of Bryophytes and Pteridophytes.
Answer: Bryophytes: 1. Funaria (Moss) 2. Marchantia (Liverwort)
Pteridophytes: 1. Marsilea 2. Ferns (such as Nephrolepis)
In simple words: Moss and liverworts are bryophytes; ferns and Marsilea are pteridophytes.

Q 24 Define advantage of using scientific name instead of common name?
Answer: The advantages of scientific names are:
1. Universality: Scientific names are universally accepted and remain the same all over the world, regardless of local languages.
2. Uniqueness: Each organism has only one valid scientific name, avoiding confusion caused by multiple local or common names for the same species.
3. Relationship indication: Scientific binomials reflect genus and species relationships, giving clues about classification.
In simple words: Scientific names prevent confusion because one universal name is used worldwide.

Exam Tip: Highlight universal acceptance and elimination of local name confusion.

Q 25 Define the main characteristics of Vertebrates.
Answer: Main characteristics of vertebrates include:
1. Presence of a true vertebral column (backbone) replacing the notochord in adults.
2. A well-developed brain protected inside a cranium (skull).
3. Bilateral symmetry, triploblastic bodies, and a true coelom.
4. Complex organ systems including a closed circulatory system with a ventral heart.
In simple words: Vertebrates have a backbone, a skull protecting the brain, and advanced organ systems.

Exam Tip: The vertebral column and cranium are the hallmark features of vertebrates.

Q 26 Bat can fly still it is placed in mammals. Why?
Answer: Although bats can fly, they possess all characteristic mammalian features: they give birth to live young ones, feed their young with milk produced by mammary glands, have body hair, possess external ears (pinnae), and have a four-chambered heart with warm-blooded physiology.
In simple words: Bats give birth to live babies, feed them milk, and have hair, which makes them mammals despite having wings.

Exam Tip: Emphasize mammary glands and live birth as the defining mammalian traits.

Q 27 Why thallophytes, bryophytes and pteridophytes are called 'cryptogams'?
Answer: They are called cryptogams because their reproductive organs are hidden (cryptos means hidden, gamos means marriage), and they do not produce flowers, fruits, or seeds. Instead, they reproduce via spores.
In simple words: They are called cryptogams because they have hidden reproductive parts and reproduce by spores instead of seeds.

Exam Tip: Connect the word cryptogams to hidden reproductive structures and spore formation.

Q 28 Show the diagrammatic representation of five-kingdom classification.
Answer: Five-Kingdom Classification:
- Kingdom Monera (Prokaryotic, unicellular)
- Kingdom Protista (Eukaryotic, unicellular)
- Kingdom Fungi (Eukaryotic, multicellular, absorptive heterotrophs)
- Kingdom Plantae (Eukaryotic, multicellular, photosynthetic autotrophs)
- Kingdom Animalia (Eukaryotic, multicellular, ingestive heterotrophs)
In simple words: Life is divided into Monera, Protista, Fungi, Plantae, and Animalia based on cell type and nutrition.

Exam Tip: Use a flowchart format in your exam to clearly depict the five kingdoms.

Q 29 Draw a flowchart to depict classification of Kingdom Plantae.
Answer: Kingdom Plantae
\(\downarrow\)
1. Cryptogams (Plants without seeds)
- Thallophyta (Algae)
- Bryophyta (Mosses)
- Pteridophyta (Ferns)
\(\downarrow\)
2. Phanerogams (Seed-bearing plants)
- Gymnosperms (Naked seeds)
- Angiosperms (Enclosed seeds / Flowering plants)
- Monocotyledons
- Dicotyledons
In simple words: Plants are split into seedless cryptogams and seed-bearing phanerogams.

Exam Tip: Draw a clean branching tree diagram for Plantae classification.

Q 30 a) Identify four features possessed by all Chordates.
b) In which class would you place any organism which has:
i. a scaly exoskeleton and a bony endoskeleton.
ii. a scaly exoskeleton and lay eggs outside water.
Answer: a) 1. Presence of notochord. 2. Dorsal nerve cord. 3. Pharyngeal gill slits. 4. Post-anal tail.
b) i. Osteichthyes (Bony fishes) or Reptilia (depending on context, but bony fishes have scales and bony skeletons; reptiles also have scales and bony endoskeletons).
ii. Reptilia (Reptiles have scales and lay cleidoic eggs on land outside water).
In simple words: Chordates have a notochord and nerve cord. Scaly egg-laying land animals belong to Reptilia.

Exam Tip: Distinguish between aquatic scaly vertebrates (fishes) and terrestrial scaly egg-layers (reptiles).

Q 31 Give one point of difference between:
i) Bilateral and radial symmetry
ii) Notochord and nerve cord
Answer: i) Bilateral symmetry: The body can be divided into identical left and right halves along only one plane. Radial symmetry: The body can be divided into identical halves along multiple planes passing through the central axis.
ii) Notochord: A flexible, rod-like supporting structure running along the dorsal side of chordates. Nerve cord: A hollow, tubular cord located dorsally that makes up the central nervous system.
In simple words: Bilateral means two matching sides, while radial means symmetrical around a center. Notochord is a support rod, while nerve cord carries nerve signals.

Exam Tip: Keep comparison points crisp and focused on structural definitions.

Q 32 (a) Name the locomotary organs of echinoderms.
(b) Distinguish between:
1. Tapeworm and earthworm
2. Mite and termite
Answer: (a) Tube feet (podia) are the locomotary organs of echinoderms.
(b) 1. Tapeworm belongs to Platyhelminthes (flatworms, unsegmented parasites), whereas earthworm belongs to Annelida (segmented worms).
2. Mite belongs to Arachnida (Arthropoda, 8-legged), whereas termite belongs to Insecta (Arthropoda, 6-legged social insects).
In simple words: Echinoderms move using tube feet. Tapeworms and earthworms belong to different worm phyla, while mites and termites have different numbers of legs.

Exam Tip: Clearly state phylum/class differences for accurate comparison.

Q 33 Point out differences between the following:
(a) Bony and cartilaginous fishes.
(b) Bilateral and radial symmetry.
(c) Notochord and nerve cord.
Answer: (a) Bony fishes have a bony skeleton and operculum; cartilaginous fishes have a cartilaginous skeleton and lack an operculum.
(b) Bilateral symmetry allows division into two equal halves along one plane; radial symmetry allows division along multiple radial planes.
(c) Notochord is a skeletal supporting rod; nerve cord is a nervous structure for signal conduction.
In simple words: Bony vs cartilage fishes differ in skeleton material; symmetry types differ in planes of division; notochord supports while nerve cord transmits impulses.

Exam Tip: Use bullet points for clear distinction in multi-part difference questions.

Q 34 Give a brief account of angiosperms.
Answer: Angiosperms are flowering seed plants in which the seeds are enclosed within fruits (ovaries). They are the most dominant and highly evolved group of land plants. They exhibit vascular tissues (xylem and phloem), produce flowers for reproduction, and are divided into two main classes: Monocotyledons (one seed leaf) and Dicotyledons (two seed leaves).
In simple words: Angiosperms are flowering plants with seeds enclosed inside fruits.

Exam Tip: Highlight flowers, enclosed seeds in fruits, and monocot/dicot divisions.

Q 35 What are the bases by which Vertebrata are divided into sub-groups?
Answer: Vertebrates are divided into sub-groups based on several key evolutionary and physiological criteria:
1. Nature of the endoskeleton (cartilage vs. bone).
2. Method of respiration (gills, lungs, or skin).
3. Structure and chambers of the heart (two, three, or four-chambered).
4. Method of reproduction and embryonic development (egg-laying oviparous vs. live-bearing viviparous).
5. Body covering (scales, feathers, or hair/fur).
In simple words: Vertebrates are grouped based on skeleton type, breathing organs, heart structure, and body coverings.

Q 36 Identify the below given organism and write four major characteristics of its phylum.
Answer: Organism identified: Leech (Phylum Annelida).
Four major characteristics of Phylum Annelida:
1. Body is segmented (metamerically segmented) both externally and internally.
2. They possess a true coelom (coelomate animals).
3. Locomotion occurs via setae or parapodia (or muscular body wall in leeches).
4. They have a closed circulatory system and bilateral symmetry.
In simple words: The organism is a segmented worm belonging to Annelida, which have true body cavities and segmented bodies.

Exam Tip: Metameric segmentation and true coelom are the most important features of Annelids.

Q 37 Identify the below given organism and give four major characteristics of its phylum:
Answer: Organism identified: Earthworm (Phylum Annelida).
Four major characteristics of Phylum Annelida:
1. Body is bilaterally symmetrical and triploblastic.
2. Presence of metameric segmentation (segments marked by ring-like grooves).
3. Coelom is a true fluid-filled body cavity.
4. Excretion is carried out by specialized coiled tubes called nephridia.
In simple words: Earthworms belong to Annelida, characterized by ringed segments, true body cavities, and bilateral symmetry.

Exam Tip: Mention segmentation and nephridia for Annelida.

Q 38 Identify the below given organism and give any four major characteristics of its phylum:
Answer: Organism identified: Planaria (Phylum Platyhelminthes / Flatworms).
Four major characteristics of Phylum Platyhelminthes:
1. Body is dorsoventrally flattened, earning them the name flatworms.
2. They are acoelomate (lack a body cavity).
3. Body organization is at the tissue level with bilateral symmetry.
4. They are mostly parasitic, though some like Planaria are free-living with high regeneration capacity.
In simple words: Planaria is a flatworm (Platyhelminthes) with a flat body and no internal body cavity.

Exam Tip: Flattened body and acoelomate nature are hallmark features of Platyhelminthes.

Q 39 Identify the below given organism and give four major characteristics of its phylum:
Answer: Organism identified: Cockroach (Phylum Arthropoda).
Four major characteristics of Phylum Arthropoda:
1. Jointed appendages (legs and antennae).
2. Exoskeleton made of tough chitin.
3. Body divided into head, thorax, and abdomen.
4. Open circulatory system with a haemocoel.
In simple words: Cockroaches belong to Arthropoda, which have jointed legs and hard outer shells.

Exam Tip: Jointed appendages and chitinous exoskeleton define Arthropoda.

Q 40 Identify the below given organism, and give four major characteristics of its phylum:
Answer: Organism identified: Octopus (Phylum Mollusca).
Four major characteristics of Phylum Mollusca:
1. Soft, unsegmented body often covered by a calcareous shell.
2. Bilaterally symmetrical with a triploblastic body.
3. Muscular foot used for locomotion.
4. Presence of a mantle cavity and a rasping feeding organ called a radula.
In simple words: Octopuses are molluscs with soft bodies, muscular feet, and bilateral symmetry.

Exam Tip: Mention muscular foot, soft body, and mantle cavity for Mollusca.

Q 41 Identify the below given organism and give four major characteristics of its phylum:
Answer: Organism identified: Ascidia / Sea squirt (Phylum Chordata, Subphylum Urochordata / Tunicata).
Four major characteristics of Phylum Chordata:
1. Presence of a notochord at some stage in life.
2. Dorsal hollow nerve cord.
3. Paired pharyngeal gill slits.
4. Post-anal tail.
In simple words: Sea squirts are chordates that possess a notochord and gill slits during their life cycle.

Exam Tip: Even though adults may lose some features, chordate larvae show the characteristic notochord and nerve cord.

Most Important Questions

Q 1 Name the character included by Aristotle for biological classification?
Answer: Aristotle classified animals based on their habitat, specifically whether they lived on land, in water, or in air.
In simple words: Aristotle grouped animals by where they lived (land, water, or air).

Exam Tip: Aristotle's simple classification was based purely on habitat.

Q 2 Name one edible fungus?
Answer: Agaricus (mushroom) is a well-known edible fungus.
In simple words: Mushrooms are edible fungi.

Q 3 Write a short note on distribution of bacteria.
Answer: Bacteria are ubiquitous, meaning they are found almost everywhere on Earth. They exist in soil, deep ocean vents, hot springs, polar ice caps, the atmosphere, and inside or on the bodies of plants and animals as symbionts or pathogens.
In simple words: Bacteria live everywhere on Earth, from extreme heat to extreme cold.

Exam Tip: Use the biological term ubiquitous when describing bacterial distribution.

Q 4 What are mycoplasma?
Answer: Mycoplasmas are the smallest known living cells that lack a rigid cell wall around their cell membrane. They are prokaryotic and can survive without oxygen.
In simple words: Mycoplasmas are tiny bacteria-like organisms that do not have cell walls.

Exam Tip: Absence of a cell wall is the key characteristic of mycoplasmas.

Q 5 What is alternation of generation?
Answer: Alternation of generation is the life cycle phenomenon in plants where a multicellular diploid sporophyte generation alternates with a multicellular haploid gametophyte generation.
In simple words: It is the shifting between spore-producing and gamete-producing stages in plant life cycles.

Exam Tip: Mention sporophyte (diploid) and gametophyte (haploid) phases.

Q 6 Who proposed five-kingdom classification? What are the names of kingdoms?
Answer: R.H. Whittaker proposed the five-kingdom classification. The five kingdoms are:
1. Monera
2. Protista
3. Fungi
4. Plantae
5. Animalia
In simple words: Whittaker classified all living things into Monera, Protista, Fungi, Plantae, and Animalia.

Exam Tip: Learn the exact spelling of all five kingdom names.

Q 7 What are the criteria used by Whittekar for five kingdom classification?
Answer: Whittaker used the following criteria:
1. Complexity of cell structure (prokaryotic vs. eukaryotic).
2. Complexity of organism body organization (unicellular vs. multicellular).
3. Mode of nutrition (autotrophic vs. heterotrophic/absorptive/ingestive).
4. Phylogenetic relationships (evolutionary history).
In simple words: He grouped organisms based on cell type, body structure, and how they get food.

Exam Tip: Cell structure and mode of nutrition are Whittaker's primary criteria.

Q 8 Draw the different shapes of bacteria.
Answer: Bacteria occur in four major shapes:
1. Coccus (Spherical)
2. Bacillus (Rod-shaped)
3. Spirillum (Spiral-shaped)
4. Vibrio (Comma-shaped)
In simple words: Bacteria can be round, rod-shaped, spiral, or comma-shaped.

Exam Tip: Name and sketch spherical, rod, spiral, and comma shapes when asked.

Q 9 What are lichens?
Answer: Lichens are symbiotic associations between a fungus (mycobiont) and an alga or cyanobacterium (phycobiont), where both organisms mutually benefit each other.
In simple words: Lichens are a partnership between fungi and algae living together.

Exam Tip: Mention the symbiotic relationship between fungus and algae.

Q 10 Write the advantages and disadvantage of binomial system of classification.
Answer: Advantages:
1. Provides a unique, universally accepted two-part name for every species.
2. Eliminates confusion caused by multiple local names.
Disadvantages:
1. Names can sometimes be long and difficult to pronounce or remember.
2. Frequent taxonomic revisions can lead to changing scientific names, causing confusion.
In simple words: Scientific names give universal clarity, but can be hard to memorize.

Exam Tip: Focus on universality as the main advantage and name complexity as a disadvantage.

Q 11 Name the amphibians of the plant kingdom?
Answer: Bryophytes are known as the amphibians of the plant kingdom because they live in damp soil but require water for sexual reproduction (fertilization).
In simple words: Bryophytes are called plant amphibians because they need water to reproduce.

Exam Tip: The dependence on water for fertilization is why bryophytes are called plant amphibians.

Q 12 Write any four common features of algae.
Answer: 1. They are simple, thalloid plants lacking true roots, stems, or leaves.
2. They are mostly aquatic (marine or freshwater).
3. They possess chlorophyll and are autotrophic (photosynthetic).
4. Their cell walls are primarily made of cellulose.
In simple words: Algae are simple water plants that make their own food and have no true roots or leaves.

Exam Tip: Thalloid body and aquatic habitat are key features of algae.

Q 13 What is the meaning of the word 'Cryptogamae'.
Answer: The word 'Cryptogamae' is derived from Greek words where 'crypto' means hidden and 'gamos' means marriage, collectively meaning plants with hidden reproductive organs.
In simple words: Cryptogamae means plants with hidden reproductive parts.

Q 14 How are angiosperms different from gymnosperms , give two main points.
Answer: 1. Seed Enclosure: Angiosperms have seeds enclosed within fruits, whereas gymnosperms have naked seeds.
2. Flowers: Angiosperms produce flowers and fruits, whereas gymnosperms do not produce flowers (their seeds are borne on cones).
In simple words: Angiosperms have flowers and covered seeds, while gymnosperms have naked seeds on cones.

Exam Tip: Flowers and seed enclosure are the primary differences.

Q 15 What are the two classes of angiosperms? What is the basis of division?
Answer: The two classes of angiosperms are Monocotyledons and Dicotyledons. The basis of division is the number of cotyledons (seed leaves) present in the seed: one cotyledon in monocots and two in dicots.
In simple words: Angiosperms are divided into monocots and dicots based on having one or two seed leaves.

Exam Tip: Cotyledon count is the exact basis of this classification.

Q 16 Name the organisms responsible for the fixation of carbon dioxide in water bodies?
Answer: Microscopic aquatic algae and phytoplankton are primarily responsible for the fixation of carbon dioxide in water bodies through photosynthesis.
In simple words: Water algae and phytoplankton fix carbon dioxide in aquatic environments.

Exam Tip: Algae and phytoplankton act as primary aquatic carbon fixers.

Q 17 How are cones formed in gymnosperms?
Answer: Cones in gymnosperms are specialized reproductive structures formed by clustered, modified leaves (sporophylls) that bear sporangia, developing into male or female strobili.
In simple words: Cones are clusters of reproductive leaves that carry seeds or pollen in gymnosperms.

Exam Tip: Cones act as reproductive organs in conifers and gymnosperms.

Q 18 Name the group of the following organisms:
(a) Sponges
(b) flatworms
Answer: (a) Sponges: Phylum Porifera
(b) Flatworms: Phylum Platyhelminthes
In simple words: Sponges belong to Porifera and flatworms belong to Platyhelminthes.

Exam Tip: Match common names with their respective phyla.

Q 19 Write two features of group arthropoda. Give an example of an arthropod.
Answer: Features of Arthropoda:
1. Presence of jointed appendages.
2. Exoskeleton made of chitin.
Example: Butterfly, Crab, or Spider.
In simple words: Arthropods have jointed legs and a hard outer shell; an example is a butterfly.

Exam Tip: Jointed legs and chitinous exoskeleton are essential arthropod features.

Q 20 What are the differences between animals belonging to the Aves group and those in the Mammalia?
Answer: 1. Body Covering: Aves have bodies covered in feathers and forelimbs modified into wings, whereas Mammals have hair or fur and external ears (pinnae).
2. Reproduction: Aves are oviparous (lay hard-shelled eggs), whereas most Mammals are viviparous (give birth to live young) and feed them milk from mammary glands.
In simple words: Birds have feathers and lay eggs, while mammals have hair and feed milk to their young.

Q 21 Distinguish between open type and closed type of circulatory system.
Answer: Open Circulatory System: Blood flows out of blood vessels into open body spaces (haemocoel) where it directly bathes organs and tissues (e.g., Arthropods).
Closed Circulatory System: Blood remains confined within a continuous network of blood vessels (arteries, veins, capillaries) and does not come into direct contact with tissue cells (e.g., Annelids, Vertebrates).
In simple words: Open systems pump blood into open spaces, while closed systems keep blood inside vessels.

Exam Tip: Focus on whether blood flows in vessels or open sinuses.

Q 22 What is notochord? How are animals divided on the basis of notochord?
Answer: A notochord is a long, flexible, rod-like supporting structure that runs along the back of chordate animals beneath the nerve cord. Based on the notochord, animals are divided into:
1. Non-chordates: Animals that do not develop a notochord at any stage.
2. Chordates: Animals that possess a notochord at least during embryonic development.
In simple words: A notochord is a flexible support rod. Animals are divided into chordates and non-chordates based on it.

Exam Tip: Define notochord as a dorsal supporting rod.

Q 23 Write any two important features found in platyhelminthes.
Answer: 1. Their bodies are dorsoventrally flattened (flatworms).
2. They are acoelomate (lack a true body cavity).
In simple words: Platyhelminthes have flat bodies and no body cavity.

Exam Tip: Flat body shape and lack of coelom are the two hallmark traits.

Q 24 Differentiate the two body forms exhibited by coelentrates.
Answer: 1. Polyp: A cylindrical, sessile (fixed) body form (e.g., Hydra, Sea anemone).
2. Medusa: An umbrella-shaped, free-swimming body form (e.g., Jellyfish).
In simple words: Coelenterates exist as fixed cylindrical polyps or free-swimming medusae.

Exam Tip: Remember polyp (sessile) vs medusa (free-swimming).

Q 25 Describe the body structure of sponges.
Answer: Sponges (Porifera) have a cellular level of organization with asymmetric or radial body plans. Their body wall is perforated by numerous pores called ostia, through which water enters a central cavity called the spongocoel and exits via an opening called the osculum. They possess a skeleton made of calcareous or silicious spicules or spongin fibers.
In simple words: Sponges are simple, pore-bearing aquatic animals with water canals.

Q 26 Describe the 4 characteristic features of the largest phylum of kingdom Animalia.
Answer: The largest phylum is Arthropoda. Its four main characteristics are:
1. Jointed appendages used for walking, feeding, and sensing.
2. Hard chitinous exoskeleton that provides protection and support.
3. Segmented body, typically divided into head, thorax, and abdomen.
4. Open circulatory system with a blood-filled haemocoel.
In simple words: Arthropods have jointed legs, hard shells, segmented bodies, and open blood systems.

Exam Tip: Jointed legs and chitinous exoskeleton are essential.

Q 27 Describe the class Mammalia.
Answer: Mammalia is a class of advanced warm-blooded vertebrate animals. Key features include:
1. Presence of mammary glands for nourishing young with milk.
2. Body covered with hair or fur.
3. Most give birth to live young (viviparous) with a few egg-laying exceptions (monotremes).
4. Possess a four-chambered heart and a neocortex brain region.
In simple words: Mammals are warm-blooded animals with hair that feed milk to their babies.

Exam Tip: Mammary glands and hair are definitive mammalian traits.

Q 28 Define bilateral symmetry?
Answer: Bilateral symmetry is a body plan in which an organism can be divided into identical left and right halves along only one specific central plane.
In simple words: Bilateral symmetry means the left and right sides are mirror images of each other.

Exam Tip: Emphasize that division into mirror images occurs along a single plane.

Q 29 Name the second largest animal phylum.
Answer: Phylum Mollusca is the second largest animal phylum after Arthropoda.
In simple words: Mollusca is the second largest animal group.

Exam Tip: Remember Arthropoda is first and Mollusca is second in species diversity.

Q 30 Which phylum shows the presence of spongin fibres in its organisms?
Answer: Phylum Porifera (sponges) shows the presence of spongin fibers and spicules that form their skeletal framework.
In simple words: Spongin fibers are found in sponges (Porifera).

Exam Tip: Link spongin fibers directly to sponges (Porifera).

Q 31 Describe coelom, ceolomate, pseudocoelomate and acopelomate.
Answer: - Coelom: The fluid-filled body cavity situated between the body wall and digestive tract, lined by mesoderm.
- Coelomate: Animals possessing a true, mesoderm-lined coelom (e.g., Annelids, Arthropods, Chordates).
- Pseudocoelomate: Animals in which the body cavity is present but not fully lined by mesoderm; instead, pouches of mesoderm are scattered (e.g., Aschelminthes / Roundworms).
- Acoelomate: Animals that completely lack a body cavity (e.g., Platyhelminthes / Flatworms).
In simple words: Coelomates have a true body cavity, pseudocoelomates have a false one, and acoelomates have none.

Exam Tip: Mesoderm lining is the critical criterion distinguishing true coeloms from pseudocoeloms.

Q 32 Identify the phylum which shows the presence of notochord, dorsal nerve chord and gill-slits?
Answer: Phylum Chordata is characterized by the presence of a notochord, dorsal nerve cord, and pharyngeal gill slits.
In simple words: These are the defining features of Phylum Chordata.

Q 33 Which phylum shows the presence of mucus glands in the skin and three chambered heart?
Answer: Phylum Chordata, specifically Class Amphibia (amphibians like frogs and salamanders), features moist skin with mucus glands and a three-chambered heart.
In simple words: Amphibians have moist skin with mucus and a three-chambered heart.

Exam Tip: Mucus glands in skin and a three-chambered heart point directly to amphibians.

Q 34 Which reptile has four-chambered heart?
Answer: Crocodiles belong to the class Reptilia and are unique among reptiles for possessing a four-chambered heart.
In simple words: Crocodiles are reptiles that have a four-chambered heart instead of a three-chambered one.

Exam Tip: Crocodiles are the classic exception to the three-chambered heart rule in reptiles.