Animals Forms and Function

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Chapter 3 : Animals Forms and Function

Animals arrow_upward

  • A living organism which feeds on organic matter, typically have specialized sense organs and nervous systems and are able to respond rapidly to stimuli.
  • Animals are generally distinguished from plants by being unable to synthesize organic molecules from inorganic molecules, so that they have to feed on plants or on other animals.

  • Vertebrates and Invertebrates arrow_upward

  • Living things are those who can move independently and that has senses for recognizing and reacting to the environment around it.
  • Animals are divided into two groups, vertebrates and invertebrates

  • Vertebrates

  • Vertebrates are the most advanced organisms on Earth.
  • The traits that make all of the animals in this section special are their spinal cords, vertebrae, and notochords.
  • It's all about having a series of nerves along your back (dorsal side).
  • It surrounds and protects the main nerve cord.
  • Our species, Homo sapiens, are included within the Vertebrata.
  • Vertebrates are easy to find and they can be seen by naked eyes.
  • Some general characteristics of vertebrates:
    • Bilateral symmetry (Body has a central axis)
    • Vertebrates have outer covering of protective cells
    • It can be modified into hairs, feathers, and scales etc.
    • They have well-developed internal skeleton.
    • Highly developed brain enclosed by a skull.
    • This provides advanced structures that are highly protected from any sort of damage.
    • Well-developed sense organs (eyes, ears, nostrils) located on the head.
    • They have respiratory system, including either gills or lungs.
  • Vertebrates include following type of organism:
    • Human
    • Fishes
    • Birds
    • Reptiles
    • Mammals
    • Underground animals
    • Amphibians


  • Invertebrates are animal species which do not have a developed vertebral column or backbone.
  • Invertebrates are generally smaller in size.
  • Most of them can’t be seen by naked eyes, they live inside the earth.
  • A vast amount of animal species are invertebrates,
  • Some general characteristics of invertebrates:
    • They have basically three body parts i.e. head, chest, and abdomen.
    • They have no lungs, respiration is through skin.
    • Invertebrates lives in colonies, they live together, and best example are ants.
    • Some invertebrates are harmful like mosquitoes.
    • All invertebrates lay eggs.

    Aquatic Animals arrow_upward

  • Animals, vertebrates or invertebrates that live in water for their whole life are aquatic animals.
  • Aquatic animals live in water for their whole life whereas we can’t live in water more than 5 min.
  • The reason behind this is they have gills to breath beneath the water.
  • They have paired fins on their body to swim into the water.
  • Aquatic animals have streamlined body, and bones are spongy and light.
  • Aquatic animals include animals living in fresh water and salt water both but specific term for animals living in the sea or oceans are marine animals.
  • All aquatic animals do not breathe inside the water some are air breathing aquatic animals.
  • Animals like whales live inside the water but they come to the surface of water and then breathe air.
  • Most of the aquatic animals lay eggs, but not all. There are some mammals that directly give birth to their young ones.
  • Animals we see on land are just 20% of whole animal kingdom whereas 80% of animals on earth live underwater.

  • Reptiles arrow_upward

  • Reptiles are members of the class Reptilian.
  • Reptiles are vertebrates
  • Snakes, lizards, turtles, crocodiles, and birds are reptiles.
  • Like all vertebrates, reptiles have bony skeletons that support their bodies
  • They can be as small as less than an inch long or as big as the saltwater crocodile, which can weigh more than a ton.
  • All reptiles have scales, but some are too small to be seen.
  • Reptiles have one most unique feature that they can maintain their body temperature according to earth’s temperature.
  • Most of them lay eggs, but a few give birth to young ones.
  • Most of the reptiles are Amphibians.
  • Amphibians are organism that can live on both land and water.
  • Most reptiles can live their entire lives on land and reproduce in dry habitats.
  • Some types of reptiles (such as sea turtles and penguins) are adapted to living in water.
  • But even these species come onto land to lay their eggs.
  • All reptiles also have lungs, so even those living in water come to the surface to breath air.

  • Mammals arrow_upward

  • Mammals are air breathing vertebrates
  • These animals are characterized by hair, three middle ear bones, and mammary glands functional in mothers.
  • All female mammals nurse their young ones with milk.
  • Milk is secreted from special glands, the mammary glands.
  • Mammal’s control heat production and the sweat glands help to cool the body.
  • All mammals have lungs and breathe dry air.
  • All mammals are warm blooded.
  • Humans are also mammals that give birth to their young ones and feed their baby with milk.
  • All mammals give birth to their young ones except Monotreme.
  • Monotreme is the type of mammal that lays eggs.
  • They are very few and rare but it specifies that all the mammals do not give birth to their young ones.
  • The mammalian heart has 4 chambers and internal temperature of mammals is generally high.
  • Most mammals walk on 4 legs, only the humans walking upright on 2 legs.
  • Aquatic mammals have flippers, or fins, for swimming rather than legs.

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