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chapter 2 biology class 7

 

Recall and Unwind

Fill in the Blanks

  1. The two-kingdom system was proposed by Carolus Linnaeus.
  2. R. H. Whittaker gave the five-kingdom classification.
  3. Bacteria belong to kingdom Monera.
  4. Kingdom Protista consists of unicellular microorganisms.
  5. Bread mould is also known as Rhizopus.

APPLY YOUR KNOWLEDGE

  1. Annelids have a soft, cylindrical and bilaterally symmetrical body.
  2. Molluscs have a soft, unsegmented body protected by one or more hard shells.
  3. Fungi are heterotrophs and feed on organic matter.
  4. Bacteria like Rhizobium live in the root nodules of leguminous plants.
  5. Vibrio cholerae causes cholera in human beings.

True/False (with Corrections)

  1. Frog is a warm-blooded animal.
    False. Correction: cold-blooded
  2. Pisces have a heart with four chambers.
    False. Correction: two chambers
  3. Amoeba belongs to Kingdom Protista.
    True
  4. Bacteria help to recycle nutrients in the soil.
    True
  5. Moulds respire anaerobically.
    False. Correction: aerobically

Choose the Correct Answer

  1. Which of the following is a fungus?
    (a) Bacteria (b) Mushroom (c) Algae (d) Amoeba
  2. Which of the following phyla consists of flattened, unsegmented worms without a body cavity?
    (a) Cnidaria (b) Arthropoda (c) Platyhelminthes (d) Nematoda
  3. Which of the following is a warm-blooded animal?
    (a) Fish (b) Crocodile (c) Human (d) Frog
  4. In which of the following animals are the forelimbs modified into wings?
    (a) Pigeon (b) Housefly (c) Human (d) Frog
  5. Which of the following animals is not an invertebrate?
    (a) Spongilla (b) Jellyfish (c) Tapeworm (d) Fish

Match the Columns

Column A

Column B

1. Kingdom Fungi

(e) Bread mould

2. Kingdom Monera

(b) Cyanobacteria

3. Kingdom Animalia

(d) Sea anemone

4. Kingdom Plantae

(c) Fern

5. Kingdom Protista

(a) Paramecium

Circle the Odd One Out and Give Reason

  1. Porifera, Earthworm, Salamander, Euglena
    Odd One: Euglena — it is single-celled, others are multicellular.
  2. Tapeworm, Liver fluke, Planaria, Earthworm
    Odd One: Earthworm — It is a segmented worm, others are unsegmented.
  3. Thallophyte, Gymnosperm, Bryophyte, Fungus
    Odd One: Fungus — It is not a plant, others are types of plants.
  4. Toad, Tortoise, Paramecium, Frog
    Odd One: Paramecium — It is unicellular, others are multicellular animals.

Answer in One Word

  1. Animals without a backbone
    Invertebrates
  2. Animals with soft, unsegmented body and hard shell
    Molluscs
  3. Phylum with the largest number of species
    Arthropoda
  4. A disease in wheat plant
    Rust
  5. Viviparous animals with hair on their bodies
    Mammals

Define the Following Terms

  1. Taxonomy
    The branch of biology which deals with the classification of organisms.
  2. Saprophytes
    Organisms that feed on dead and decaying organic matter.
  3. Vertebrates
    Animals with a backbone.
  4. Amphibians
    Animals that live both on land and in water.
  5. Multiple fission
    A reproductive process in which a single organism divides to form many daughter organisms.

Answer the Following Questions In Brief

  1. What are the disadvantages of two-kingdom classification?
    • It classified organisms only as plants or animals, which is inadequate for many organisms, e.g., Euglena has features of both plants and animals.
    • Fungi were included with plants though they do not have characteristics of plants.
    • It does not address organisms with mixed or unique features, leading to confusion and inaccuracy.
  2. Differentiate between Kingdom Monera and Kingdom Protista.

Kingdom Monera

Kingdom Protista

Prokaryotic organisms (no true nucleus)

Eukaryotic organisms (true nucleus)

Always unicellular

Mostly unicellular, some multicellular

Example: Bacteria, blue-green algae

Example: Amoeba, Euglena, Paramecium
  1. What are the two important features of mollusca?
    • They have a soft, unsegmented body protected by a hard shell.
    • They have a soft muscular foot which helps in locomotion.
  2. Name the major phyla of invertebrates.
    Porifera, Cnidaria, Platyhelminthes, Nemathelminthes, Annelida, Arthropoda, Mollusca, Echinodermata.
  3. Describe the body of a snail.
    A snail has a soft, unsegmented body covered by a hard shell for protection and a soft muscular foot for movement.

Answer the Following Questions in Detail

  1. Write three advantages and three disadvantages of bacteria.

Advantages:

    • Saprophytic bacteria decompose dead matter, enriching the soil.
    • Some bacteria fix nitrogen in root nodules of leguminous plants.
    • Used for food production (e.g., curd, cheese, vinegar).

Disadvantages:

    • Some bacteria cause diseases like tuberculosis, typhoid, and cholera.
    • They can spoil food, causing it to rot and become unsafe to eat.
    • Cause diseases in plants, reducing crop yield.
  1. Write the features of amphibians and reptiles.

Amphibians:

    • Live both on land and in water;
    • Lay eggs in water (oviparous).
    • Have thin, moist skin; three-chambered heart; cold-blooded.

Reptiles:

    • Mostly live on land; some in water.
    • Have dry skin with scales; lay eggs on land with leathery shells.
    • Breathe through lungs; generally three-chambered heart; cold-blooded.
  1. What are the features of birds that allow them to fly?
    • Streamlined body and feathers reduce air resistance.
    • Forelimbs modified into wings; bones are light and hollow.
    • Powerful flight muscles attached to the breastbone; beaks present (no teeth).
  2. What are the uses of fungi?
    • Decompose dead and decaying matter, recycling nutrients into the soil.
    • Yeast is used in making bread, idli, dosa, wine, and beer.
    • Source of antibiotics (Penicillium produces penicillin).
  3. Explain nutrition and reproduction in amoeba.

Nutrition:
Amoeba engulfs food particles by extending pseudopodia around them to form a food vacuole. Digestive juices break down the food, the digested part is absorbed, and the undigested part is ejected out.

Reproduction:
Amoeba reproduces mainly by binary fission (splitting into two daughter amoebae under favorable conditions) and multiple fission (producing many daughter cells during unfavorable conditions when it forms a cyst).

Build Your Skills

Picture-based questions require the actual images shown in your book for completion, but here is the structure:

  1. [Identification and classification based strictly on what is visible in the book’s images and matching descriptions.]

Observe and Answer

  1. Image P is a disease caused in crops. It belongs to Kingdom Fungi.
  2. Another disease caused in the same plant is Smut (another example: "red rot of sugar cane", "blight of potato" as described in the text).
  3. Yeast is used to make the food items in image Q; it uses sugar as food and breaks it down into carbon dioxide and alcohol.
  4. Image P shows the microorganism can be parasitic; Q shows the microorganism can be useful.

Make It Error-free

Correct the passage:

Incorrect

Correct

multicellular

unicellular

Fungi

Protista

prokaryotic

eukaryotic

tail-like projections

finger-like projections (pseudopodia)

cell wall

cell membrane

nitrogen gas

carbon dioxide

sexually

asexually

singular

binary

HOTS Corner

  1. What will happen if we keep a slice of bread in a warm moist place for 3–4 days?
    • Bread mould appears (a cotton-like growth), which belongs to Kingdom Fungi. The bread is not suitable for consumption as it’s spoiled by fungi.
  2. Why was a spoon of curd mixed in warm milk and why did the taste turn sour?
    • The curd contains Lactobacillus bacteria, which convert lactose to lactic acid and set the curd. If not refrigerated, bacteria continue growing, making the curd sour due to excess lactic acid.
  3. An organism is an invertebrate, fixed to the bottom of the pond, with pores all over its body. In which phylum does it belong?
    • Phylum Porifera.

Case Study: Kingdom Monera

  1. Characteristics of organisms belonging to Kingdom Monera:
    • Unicellular, prokaryotic; no true nucleus or membrane-bound organelles; can be autotrophic or heterotrophic.
  2. Examples of bacteria by shape:
    • Cocci: Streptococcus pneumoniae, Neisseria gonorrhoeae.
    • Vibrio: Vibrio cholerae.
  3. Shape of Lactobacillus:
    • Rod-shaped (bacillus).
  4. What are saprophytic bacteria?
    • Bacteria that decompose or break down dead plants and animals into simpler substances, returning nutrients to the soil.
  5. Difference between gram-positive and gram-negative bacteria:
    • Gram-positive bacteria retain violet stain due to thick cell wall.
    • Gram-negative bacteria do not retain violet stain; thinner cell wall and extra outer membrane.

 
























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