Features of Organisms - 1 | Biology for GCSE/IGCSE - Year 11 PDF Download

The Five Kingdoms

• Living organisms are initially categorized into five distinct kingdoms, namely: Animals, Plants, Fungi, Protoctists, and Prokaryotes.
• These kingdoms represent the primary division in the classification system, each encompassing various types of organisms.
• Animals:
  • Characterized by multicellularity, animals have cells with a nucleus but lack cell walls and chloroplasts.
  • They predominantly rely on consuming organic substances produced by other living beings for sustenance.
• Plants:
  • Plants typically possess cell walls, chloroplasts, and a nucleus within their cells.
  • They are known for their ability to photosynthesize, converting sunlight into energy through chlorophyll.
• Fungi:
  • Fungi are characterized by their unique mode of nutrition, absorbing nutrients from their surroundings.
  • They play a crucial role in ecosystems by decomposing organic matter and recycling nutrients.
• Protoctists:
  • Protoctists encompass a diverse group of single-celled organisms with distinct features.
  • These organisms can exhibit characteristics of both plants and animals, showcasing versatility in their biology.
• Prokaryotes:
  • Prokaryotes represent simple, single-celled organisms lacking a distinct nucleus.
  • They are ubiquitous in various environments and play essential roles in biochemical processes.

Main Features of Animal and Plant Cells

Animal Cells:

• They are multicellular organisms.
• Each cell contains a nucleus but lacks cell walls or chloroplasts.
• They derive nutrients from organic substances produced by other living organisms.

Plant Cells:

• They are multicellular organisms.
• Each cell contains a nucleus, chloroplasts, and cellulose cell walls.
• They obtain energy through photosynthesis.

The Animal Kingdom

• Organisms in the animal kingdom are grouped based on several main features.

Vertebrates

• Vertebrates are characterized by having a backbone.
  • There are 5 classes of vertebrates.

Invertebrates

• Invertebrates do not have a backbone.
• One way to classify invertebrates is based on whether they have legs or not.
• All invertebrates with jointed legs belong to the phylum Arthropods.
• Arthropods are further classified into specific classes: