Database results:
examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Animal Characteristics and Examples
Animals are a diverse group of living organisms that share certain key characteristics. Unlike plants, animals cannot make their own food and must consume other organisms for energy. In this session, we'll explore what makes an animal an animal and how we classify the incredible variety of animal life on Earth.
Key Definitions:
All living organisms, including animals, share seven key characteristics summarised by the acronym MRS GREN:
Unlike other organisms, animals typically:
Scientists classify animals into groups based on their shared characteristics. The main division in the animal kingdom is between vertebrates (animals with backbones) and invertebrates (animals without backbones).
Vertebrates make up only about 3% of all animal species but include the largest and most familiar animals. All vertebrates have a backbone (vertebral column) and an internal skeleton.
The platypus challenges our classification system! It's a mammal that lays eggs instead of giving birth to live young. It has fur like other mammals and produces milk for its young, but it also has a duck-like bill and venomous spurs on its hind legs. This unusual combination of features makes it a fascinating example of how nature doesn't always fit neatly into our classification boxes.
Invertebrates make up about 97% of all animal species. They lack a backbone and include a wide variety of animals with different body plans.
When identifying and classifying animals, scientists look at several key features:
Cold-blooded (ectothermic) animals like fish, amphibians and reptiles cannot regulate their body temperature internally. Their body temperature changes with the environment.
Warm-blooded (endothermic) animals like birds and mammals maintain a constant body temperature regardless of the environment.
Oviparous animals lay eggs (most fish, amphibians, reptiles, birds and some mammals).
Viviparous animals give birth to live young (most mammals).
Ovoviviparous animals develop eggs inside the body and give birth to live young (some fish and reptiles).
Bilateral symmetry: The body can be divided into matching halves by a single plane (vertebrates, arthropods).
Radial symmetry: The body parts are arranged around a central axis (starfish, jellyfish).
Cuttlefish are masters of disguise! These molluscs can change their skin colour and texture in an instant to match their surroundings. They have three hearts, blue-green blood and are considered among the most intelligent invertebrates. They can solve puzzles, learn from observation and use sophisticated hunting strategies. Despite their name, they're not fish at all but are related to octopuses and squids.
Animals have evolved various adaptations to survive in their environments:
The animal kingdom is incredibly diverse, with species ranging from microscopic organisms to the largest creatures on Earth. By understanding the characteristics and classifications of animals, we can better appreciate the complexity and beauty of life on our planet.
Remember that classification is a human-made system that helps us organise and understand the natural world. As we discover more about animals and their relationships, our classification systems continue to evolve.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.