Download Chp 6. Autotrophs - AdventuresinScienceEducation

V.C.E. Biology Unit 1
Autotrophs are producers
Requirements of Living Things
• Energy – all life requires a source of energy
• Oxygen – organisms require oxygen for cellular
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respiration
Water – required for growth, maintenance and
repair
Nutrients – required for growth, maintenance
and repair
Waste removal – many harmful by-products
result from the cells chemical processes
Reproduction – organisms need to replace
themselves
Autotrophs and Heterotrophs
• Autotrophs are organisms that are able to
make their own organic molecules they
need from simple inorganic molecules –
they are self feeders.
• Heterotrophs are unable to synthesise
their own organic molecules, they must
eat other living things.
Autotrophs
• Most autotrophs are plants that create
organic molecules (glucose) through a
process known as photosynthesis which
occurs in specialised cell organelles called
chloroplasts.
• Some bacteria are able to produce organic
molecules from inorganic molecules in a
process called chemosynthesis.
Photosynthesis
• Plants make the organic material, glucose, from simple
inorganic molecules, carbon dioxide and water, in the
presence of light energy and chlorophyll. This allows for
the conversion of light energy into stored chemical
energy for use by the plant.
Light energy
6CO2 + 12H20 Æ C6H12O6 + 6H20 + 6O2
chlorophyll
Photosynthesis/Cellular Respiration
• Autotrophs use energy twenty four hours a day
– using oxygen to break down glucose to release
the energy and produce water and carbon
dioxide.
• By day this is balanced by the photosynthesise
that occurs – using carbon dioxide and water to
produce glucose and oxygen.
• At low light levels the plant must take up oxygen
for cellular respiration, but at higher light levels
the plant produces excess oxygen through
photosynthesis.
Structural Adaptations
• Plants have evolved many adaptations to collect
light more efficiently.
• Obviously leaves at the end of stems and
branches allows the plant to collect more light
than merely growing along the ground.
• Dorsiventral leaves – one side has all the
chlorophyll containing cells the other has none
or few.
• Isobilateral leaves – hang vertically reducing
heat absorption, but chlorophyll is present on
both sides of the leaf
Other Nutritional Requirements
• Plants need other nutrients also. Just like
animals they need to be able to make lipid
based membranes and nitrogen based proteins
and hormones.
• Nitrogen is abundant on Earth, but mostly found
in the atmosphere in a form that organisms can’t
use. Many plants have formed symbiotic
relationships with bacteria that live in the roots
and convert the nitrogen into a useable form.
Other Nutritional Requirements
• Mineral Salts.
Plants need elements such as nitrogen,
phosphorous, potassium, sulfur, calcium and
magnesium in large quantities for making
proteins and many cell processes. These are
called the macronutrients.
They also need micronutrients such as iron, boron
and zinc in small amounts.
These are drawn up from the soil by the roots