Biology: Animal Characteristics and Classification

An animal is a living organism that is heterotrophic (cannot produce its own food) and multicellular.
Animals are eukaryotic, meaning their cells have a true nucleus.
They are capable of movement and responding to stimuli.
Animals can be found in various shapes, sizes, and habitats.

Kingdom Animalia is divided into several phyla, including:
- Chordata (vertebrates and some invertebrates)
- Arthropoda (insects, arachnids, and crustaceans)
- Mollusca (squids, octopuses, and shellfish)
- Echinodermata (starfish, sea urchins, and sea cucumbers)
Subgroups within phyla include classes, orders, families, genera, and species.

Animals can have:
- Radial symmetry (body parts arranged around a central axis)
- Bilateral symmetry (body parts arranged on both sides of a central axis)
Body cavities:
- Coelom (fluid-filled cavity between body wall and digestive system)
- Pseudocoelom (fluid-filled cavity between body wall and digestive system, but not completely lined with mesoderm)
Body systems:
- Nervous system (sensory and motor functions)
- Circulatory system (blood circulation and oxygen delivery)
- Respiratory system (breathing and gas exchange)
- Digestive system (food intake, digestion, and nutrient absorption)

Animals are heterotrophic, meaning they obtain energy from consuming other organisms or organic matter.
Types of nutrition:
- Herbivory (plant-based diet)
- Carnivory (animal-based diet)
- Omnivory (both plant- and animal-based diet)
Digestive processes:
- Mechanical digestion (breaking down food into smaller pieces)
- Chemical digestion (breaking down food into nutrients)

Modes of reproduction:
- Sexual reproduction (involving gametes and fertilization)
- Asexual reproduction (involving only one parent)
Developmental stages:
- Zygote (fertilized egg)
- Embryo (early developmental stage)
- Larva (juvenile stage)
- Adult (mature stage)

Animals are heterotrophic multicellular living organisms that cannot produce their own food.
They are eukaryotic, meaning their cells have a true nucleus.
Animals are capable of movement and responding to stimuli.
They can be found in various shapes, sizes, and habitats.

Kingdom Animalia is divided into several phyla, including Chordata, Arthropoda, Mollusca, and Echinodermata.
Chordata includes vertebrates and some invertebrates.
Arthropoda includes insects, arachnids, and crustaceans.
Mollusca includes squids, octopuses, and shellfish.
Echinodermata includes starfish, sea urchins, and sea cucumbers.
Phyla are further divided into classes, orders, families, genera, and species.

Animals can have radial or bilateral symmetry.
Radial symmetry means body parts are arranged around a central axis.
Bilateral symmetry means body parts are arranged on both sides of a central axis.
Animals have body cavities, including coelom and pseudocoelom.
Coelom is a fluid-filled cavity between the body wall and digestive system.
Pseudocoelom is a fluid-filled cavity between the body wall and digestive system, but not completely lined with mesoderm.
Animals have body systems, including nervous, circulatory, respiratory, and digestive systems.
The nervous system is responsible for sensory and motor functions.
The circulatory system is responsible for blood circulation and oxygen delivery.
The respiratory system is responsible for breathing and gas exchange.
The digestive system is responsible for food intake, digestion, and nutrient absorption.

Animals are heterotrophic, meaning they obtain energy from consuming other organisms or organic matter.
Types of nutrition include herbivory, carnivory, and omnivory.
Herbivory involves a plant-based diet.
Carnivory involves an animal-based diet.
Omnivory involves both plant- and animal-based diet.
Digestive processes include mechanical and chemical digestion.
Mechanical digestion involves breaking down food into smaller pieces.
Chemical digestion involves breaking down food into nutrients.