Classification of Organisms: Kingdom Characteristics

This document outlines the characteristic features of the four major kingdoms: Protista, Fungi, Plantae, and Animalia, as required for Cambridge A-Level Biology 9700.

Kingdom Protista

Protista is a diverse group of eukaryotic organisms that do not fit neatly into the other kingdoms. They are generally unicellular, but some are multicellular. They exhibit a wide range of characteristics, making it difficult to define a single unifying feature.

Key Characteristics:

• Mostly unicellular, but some are colonial or simple multicellular.
• Eukaryotic: Possess a true nucleus and other membrane-bound organelles.
• Diverse modes of nutrition: Autotrophic (photosynthetic), heterotrophic (phagocytosis, absorption, ingestion), and mixotrophic.
• Diverse reproductive strategies: Asexual (binary fission, budding) and sexual (conjugation, gamete fusion).
• Habitat: Found in a variety of environments including freshwater, saltwater, and soil.

Examples: Amoeba, Paramecium, Euglena, Diatoms, Algae.

Kingdom Fungi

Fungi are eukaryotic, heterotrophic organisms that obtain nutrients by absorption. They are typically multicellular, composed of hyphae (filaments) that form a mycelium.

Key Characteristics:

• Eukaryotic: Possess a true nucleus.
• Heterotrophic: Obtain nutrients by absorption of organic matter.
• Multicellular: Typically composed of hyphae.
• Cell walls made of chitin.
• Reproduce asexually (spores) and sexually (spores).
• Decomposers: Play a crucial role in nutrient cycling.

Examples: Yeast, Molds, Mushrooms, Toadstools.

Kingdom Plantae

Plantae are multicellular, eukaryotic organisms that are primarily autotrophic, meaning they produce their own food through photosynthesis.

Key Characteristics:

• Eukaryotic: Possess a true nucleus.
• Autotrophic: Perform photosynthesis using chlorophyll.
• Multicellular: Composed of cells with specialized functions.
• Cell walls made of cellulose.
• Reproduction: Both sexual (alternation of generations) and asexual.
• Habitat: Primarily terrestrial, but some are aquatic.

Examples: Mosses, Ferns, Conifers, Flowering Plants.

Kingdom Animalia

Animalia are multicellular, eukaryotic organisms that are heterotrophic, meaning they obtain nutrients by ingestion. They are characterized by their ability to move and respond to stimuli.

Key Characteristics:

• Eukaryotic: Possess a true nucleus.
• Heterotrophic: Obtain nutrients by ingestion.
• Multicellular: Composed of specialized cells organized into tissues, organs, and organ systems.
• Lack cell walls.
• Reproduction: Primarily sexual.
• Motility: Most animals are capable of movement at some point in their life cycle.

Examples: Invertebrates (e.g., insects, worms, molluscs) and Vertebrates (e.g., fish, amphibians, reptiles, birds, mammals).

Summary Table

Kingdom	Cell Type	Cell Wall	Nutrition	Body Plan	Motility	Examples
Protista	Eukaryotic	Variable	Autotrophic, Heterotrophic, Mixotrophic	Unicellular or simple multicellular	Variable	Amoeba, Paramecium, Euglena
Fungi	Eukaryotic	Chitin	Heterotrophic (absorption)	Multicellular (hyphae)	Non-motile	Yeast, Molds, Mushrooms
Plantae	Eukaryotic	Cellulose	Autotrophic (photosynthesis)	Multicellular	Non-motile (generally)	Mosses, Ferns, Flowering Plants
Animalia	Eukaryotic	Absent	Heterotrophic (ingestion)	Multicellular (tissues, organs, systems)	Motile	Insects, Worms, Fish, Mammals