Transcript Lesson 8. Autotrophs and Photosynthesis

Chapter 5: Obtaining energy and
nutrients for life
•
•
•
•
•
Heterotrophs and autotrophs
Autotrophs and photosynthesis
Heterotrophs and food
The digestive system
Digestion in animals
Today’s lesson
• Heterotrophs and autotrophs
• Autotrophs and photosynthesis
Autotrophs
• Plants
• Algae
Autotrophs
• Soak up sunlight to gain energy they
need for living (photosynthesis)
• Build their organic matter from simple
inorganic matter taken up from their
surroundings
• Terrestrial autotrophs (air and soil)
• Aquatic autotrophs (water)
Heterotrophs
• All animals
• All fungi
• Some bacteria
Heterotrophs
• Obtain energy for living and material for building
and repairing their structure from organic matter
in their surroundings
• Organic matter used by heterotroph is its food
Autotrophs
and
photosynthesis
Autotrophs and photosynthesis
• Plants algae and some protists
(phytoplankton) can make organic
molecules (sugar) by photosynthesis
• Energy is obtained from sunlight
• Organisms that can do this are autotrophic
• Photosynthesis occurs in the chloroplasts,
found in the cytosol of some cells.
Ins and outs of photosynthesis
•
•
Sunlight is converted to chemical energy
in sugars
2 sets of reactions
1. First set of reactions depends on the
availability of light and presence of chlorophyll
2. Second set of reactions does not depend on
light but depends on products from the first set
of reactions
First set of reactions
Sunlight
oxygen + hydrogen ions
Water + ADP
Chlorophyll
ADP = Adenosine diphosphate
ATP = Adenosin triphosphate
+ ATP
Second set of reactions
Carbon dioxide
+ hydrogen ions
+ ATP
Glucose + ADP
ADP = Adenosine diphosphate
ATP = Adenosin triphosphate
Where does Carbon dioxide come from?
Combining the two
• ATP and ADP are used during the
reactions (chemical energy)
End result:
Sunlight
Carbon dioxide
+ water
Glucose + oxygen
Chlorophyll
Sunlight
6CO2 + 6H20
C6H12O6 + 6O2
What makes it all happen?
• Sunlight provides the energy required to
drive the first reaction
• The ATP produced from the first reaction is
a high-energy compound that provides
energy that drives the second set of
reactions
• This leads to the production of glucose
from the carbon dioxide and hydrogen ions
Plant structures in relation to
photosynthesis
• Certain characteristics exist in plants
which enable photosynthesis to occur
• Leaves, trunk and roots
Leaves
• Flat shape- provides large surface area
exposed to sunlight
• Chloroplasts- enables it to trap energy
from sunlight
• Stomata (pores) on leaf surface provide
access into leaf for carbon dioxide
• Thinnes- diffusion of carbon dioxide to
photosynthetic cells in the leaf tissue
• Vascular tissue and xylem vesselstransport water and other compounds
Stems
• Xylem vessels and fibres give rigidity to a
stem and assist upright stance
• Branching of stems allows layers of
leaves, increasing total surface area
• Xylem vessels transport water and
minerals from roots to all aerial parts of
plant
• Phloem transports products of
photosynthesis
Roots
• Extensive root systems taps a significant
volume of soil for water and mineral salts
• Root hairs- increases area available for
absorption of water and mineral salts
• Oxygen from air in soil diffuses through
root hairs into plants
• All the characteristics of leaves, stems and
roots ensure that these structures combine
to provide the sunlight energy, carbon
dioxide and water that a plant requires for
photosynthesis
• In other words, it enables the plant to get
what it needs for the reactions to take
place efficiently
Summary
• Heterotrophs- all animals, fungi, bacteria
• Autotrophs- all plants, algae, some bacteria
• Autotrophs make their own organic material from
inorganic substances (using sunlight)
• Heterotrophs rely on food, organic matter
• Photosynthesis- converting energy of sunlight to
chemical energy in sugars
• Raw materials of photosynthesis are carbon
dioxide and water, products are sugar and O2
• Structures of various parts of plants maximise
plant’s ability to obtain raw materials necessary
for photosynthesis