The Nature and variety of living organisms

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The Nature and variety of living organisms

• IGCSE Biology

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Syllabus

• a) Characteristics of living organisms
• Recall that living organisms share the following
  basic characteristics
• b) Variety of living organisms
• Understand that there is a wide variety of living
  organisms and that modern biology classifies
  organisms on the basis of their structure and how
  they function
• Describe the common features shared by organisms
  within the five main groups, plants, animals,
  fungi, bacteria and viruses and for each group
  describe examples and their features.

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What are the differences between the living and
non-living things on this page?
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Characteristics of living things

• Movement
• Respiration
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition

Change in position by the action of muscles in
animals, and slow growth movements in plants
The process by which living cells release energy
from organic molecules
The ability to detect and respond to changes in
the environment either inside or outside the
organism
Increase in size and mass
Creation of new organisms that are the same
species as the parents
Removal of wastes from the organisms body.
Supplies an organism with the food it needs to
respire, grow, repair and reproduce.
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Classification

• Scientists classify organisms into categories
  (groups) to
• make it easier to study them
• communicate with scientists from other country.
• Classified based on their structure and how they
  function

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Classification

• Organized using a hierarchical system introduced
  by Carolus Linnaeus
• Seven taxa groups Kingdom, Phylum, Class,
  Order, Family, Genus and Species
• Taxonomists study organisms to determine which
  group they will go in.

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Classification

• Linnaeus also introduced the bionomial
  nomenclature system
• This is where all living things were given two
  names written in Latin.
• The first is the Genus name, always with a
  capital letter
• The second is the species name, always small
  letter
• Example
• Homo sapien (human)
• Canis lupus (wolf)
• Equus burchelli (zebra)
• When you write the scientific name of an organism
  you should either write it in italics (computer)
  or underline it (hand written)

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Kingdoms

• 5 Kingdoms
• Bacteria (Prokaryotae - includes bacteria and
  blue-green algae)
• Some scientists have separated this group into 2
  different kingdoms
• Protoctist (algae and protozoans)
• Fungi
• Plantae
• Animalia
• Virus

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Bacteria

• Examples bacteria and cyanobacteria
• Unicellular (single-celled) or filamentous
• No nucleus
• Circular DNA (plasmid)
• Cell wall present

Source of diagramshttp//srs.dl.ac.uk/Annual_Repo
rts/AnRep01_02/anthrax-bacteria.jpg http//www.res
a.net/nasa/images/bacteria/cyano.jpg
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Protoctist

• Examples algae, protozoans (Amoeba, Paramecium
  etc.)
• Unicellular or simple multicellular organisms
• Nucleus present
• Can photosynthesize or absorb food

Source of diagrams http//teachart.msu.edu/pila/i
mages/amoeba.jpg http//www.apocalypse.org/pub/u/j
en/red-algae.jpg
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Fungi

• Examples yeast, mushroom, mould fungi
• Cell wall made of chitin
• Nucleus present
• No chlorophyll
• Absorb food

Source of diagrams http//genetics.med.harvard.ed
u/winston/yeast20photo20copy.gif www.wussu.com/
shrooms/images/p_will1.jpg
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Plantae

• Examples grasses, oak tree, dandelions, moss,
  conifers
• Multicellular
• Cell wall present
• Chlorophyll present photosynthesis

Source of diagramswww.its.caltech.edu/.../sequoia
03-Images/8.jpg http//www.jointedgoatgrass.org/P
hotos/wheat20closup.jpg http//www.cees.iupui.ed
u/research/restoration/arbor/Images/Vegetation_Sur
vey/2002-04-16_common-dandelion.jpg
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Flowering Plants

• Monocotyledons
• Eg. Grasses, iris
• Parallel veins
• Narrow leaves
• 1 leaf in the seed
• Dicotyledons
• Eg. Sunflower, willow tree
• Broad leaves
• Veins branching
• 2 leaves in the seed

Source of diagrams http//w3.goodnews.net/kkrugh
/garden/siberian20iris2004.jpg www.jmgkids.com/m
edia/willow-tree.jpg
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Other Plants

• Moss and liverworts
• No xylem
• No roots
• Asexual and sexual stages to lifecycle
• Conifers
• Needle-like leaves
• Cone-bearing plants
• Ferns
• Reproduce using spores

Source of diagrams www.jonbarkerpics.co.uk/new20
poppy/moss20on... http//plants.montara.com/List
Pages/thumbs1/polmin0.jpg
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Animalia

• Examples ants, horses, snails, humans, whales
• Multicellular
• Nucleus present, no cell wall
• Heterotrophic (cannot make their own food)

Source of diagrams http//www.jarandi.com/photos/
whale.jpg http//animals.timduru.org/dirlist/giraf
fe/SDZ_0079-Giraffe.jpg http//www.mongabay.org/im
ages/grandcanyon/0617_fire_ant_01.jpg
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Virus

• Non-living and living
• Smallest
• Smaller than bacteria
• Parasitic
• Reproduce inside a host
• Protein coat
• Contain either DNA or RNA strand

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Arthropods

• Insects
• 3 body segments
• 3 pairs of legs
• 2 pairs of wings
• antennae
• Crustaceans
• More than 4 pairs of jointed legs
• 2 pairs of antennae
• Breathe through gills

• Arachnids
• - 2 body segments
• - 4 pairs of legs
• - No wings
• - No antennae
• Myriapods
• - One pair of antennae
• - many segments of body
• - Many pairs of legs

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Other invertebrates

• Annelids
• Long segmented body covered with mucus
• Chaetae (bristles) present
• Molluscs
• Animals with soft, unsegmented body, may have
  shell
• No limbs
• Foot present
• Nematoda
• Long thin bodies with no rings
• No legs
• No obvious head

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Vertebrates

• Mammals
• Live mainly on land
• Have fur or hair
• Mammary glands
• Birds (Aves)
• Feathers
• wings
• Fish (Pisces)
• Gills
• Skin covered with scales
• fins
• Reptiles
• Scaly skin (dry)
• Amphibians
• Smooth, moist skin

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Adaptations

• Bacteria
• Eg. Flagellum, used to move
• Single cell (less complex), so they can live in
  extreme conditions (can live in 60C temperature
  of mineral hot-springs)
• Viruses
• Eg. Very, very small so can easily be transferred
  to a host.
• DNA free (not in nucleus), so can easily be
  copied within host cell and therefore more
  viruses can be made.
• Fungi
• Eg. Hyphae used to grow through whatever the
  fungus is feeding on.

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Dichotomous keys

• Used by scientists to identify unknown organisms
• Keys consist of a series of choices that lead the
  user to the correct name of a given item.
• "Dichotomous" means "divided into two parts".
• Therefore, dichotomous keys always give two
  choices in each step.