Tuesday, 30 June 2015

Kingdom Animalia - Invertebrates and Vertebrates

Activity 2: Key Characteristics of the Organisms in the 5 Kingdoms
Special Characteristics of the Kingdom Animalia - Invertebrates and Vertebrates

done by: nishtha, durwa, wei-san, clement, everi

There are around 9 to 10 million species of animals, and about 800,000 species are identified. Fossil records of animals were found in the era of the Cambrian explosion, about 540 million years ago. Animals are divided into various sub-groups, biologists have identified about 36 phyla within the animal kingdom including birds, mammals, reptiles, fish, amphibians etc.

  • Animals are eukaryotic (organisms whose cells contain a nucleus and other organelles enclosed within membrane), multicellular and heterotrophic (organisms that cannot manufacture its own food and instead obtains its food and energy by taking in organic substances, usually plant or animal matter).
  • Habitat - Most of the animals inhabit seas, fewer are seen in fresh water and even fewer on land.
  • Size - The sizes of animals ranges from few-celled organism like the mesozoans to animals weighing many tons like the blue whale.
  • Animal bodies - Bodies of animals are made of cells organized into tissues which perform specific functions. In most animals, tissues are organized into complex organs, which form organ systems that aids in performing specific functions and then a whole body.
  • Cell structure - The animal cell contains organelles like the nucleus, mitochondria, Golgi complex, ribosomes, endoplasmic reticulum, lysosomes, vacuoles, centrioles, cytoskeleton which all have specific functions to do.
  • Body symmetry - Most of the animals are bilaterally symmetrical, while primitive animals are asymmetrical and cnidarians (jellyfish for example) and echinoderms (starfish for example) are radially symmetrical.
  • Locomotion - Most animals are motile, they show rapid movement when compared to plants and other organisms.
  • Some animal’s skin is also used for respiration.
  • Digestion - Animals ingest food, and digestion takes place in the internal cavity like the digestive system in animals. In primitive animals, vacuoles are for digestion.
  • Most animals reproduce sexually, by the fusion of haploid cells like the eggs and the sperms.
  • Invertebrates do not have a backbone, are the simplest of animals, greatest in number, most are found in water, some have exoskeleton (like starfish) and others have no skeleton (annelids).

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