Chapter 3 : Animals Forms and Function
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.
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
Topics covered in this snack-sized chapter:
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.
Vertebrates include following type of organism:
- They have respiratory system, including either gills or lungs.
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.
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 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 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.