World of Life

World of Life

Overview of Life on Earth

  • All known life forms exist on Earth, in habitats ranging from the deepest oceans to the highest mountains.
  • Biodiversity refers to the variety of life on Earth, including the different species, the genetic differences within those species, and the different ecosystems they form.
  • Eukaryotes (including animals, plants, fungi, and protists) and prokaryotes (bacteria and archaea) feature in the classification of life.

Animal Kingdom

  • Animals are multicellular, eukaryotic organisms that are part of the Animalia kingdom.
  • Animals are heterotrophic, meaning they obtain energy by consuming other organisms.
  • The classification of animals includes invertebrates and vertebrates; further divided into birds, mammals, fish, reptiles, and amphibians.

Plant Kingdom

  • Plants are multicellular, eukaryotic organisms, part of the Plantae kingdom.
  • Plants are autotrophic and use sunlight to produce food through photosynthesis.
  • Major groups include flowering plants, conifers, ferns, mosses, and green algae.

Micro-organisms

  • Micro-organisms or ‘microbes’, are organisms that can only be seen under a microscope. These include bacteria, viruses, and fungi.
  • Bacteria are prokaryotes and vital for ecological balance; some can cause diseases.
  • Viruses are infectious agents that can only replicate in the living cells of a host organism.
  • Fungi are a group of eukaryotic organisms that includes microorganisms such as yeast and moulds.

Human Body Systems

  • The nervous system controls and communicates information throughout the body.
  • The circulatory system circulates blood, delivering nutrients and oxygen to cells.
  • The respiratory system handles the intake of oxygen and removal of carbon dioxide.
  • The digestive system breaks down food, absorbs nutrients, and removes waste.
  • The immune system defends the body from potential harmful microorganisms.

Reproduction and Life Cycles

  • Reproduction can occur sexually (involving two parents and combines their genetic material) or asexually (one parent and identical genetic material).
  • All organisms have a life cycle, going from birth, growth, maturity and reproduction before eventual death.
  • Human life cycle stages include infancy, childhood, adolescence, adulthood, and old age.