Download chapter 4 - mscyr11biology

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CHAPTER 4-COMMON REQUIREMENTS OF LIVING THINGS:
SINGLE CELLS AND PLANTS
Many organisms are found in the same environment, such as a river or fish pond, but need
different requirements - Plants, animals, single celled organisms, bacteria. These requirements
are obtained in different ways, depending on the organism.
Energy is a basic need of every organism.
Autotrophs – can use the suns energy to manufacture their own energy, via photosynthesis.
- contain chlorophyll pigments
- plants, trees, shrubs …
Heterotrophs – rely on autotrophs to provide energy in package form
- animals …multicellular [like humans, birds] and single celled org,s [like
paramecium]
PARAMECIUM - A SINGLE CELLED ORGANISM
Single celled, found in still or slow moving water, even fish tanks.
Nutrients obtained directly from environment, covered in cilia that synchronise their
movement to sweep food, such as bacteria and algae into the gullet. Food eventually breaks
off forming a food vacuole that is processed by the paramecium. H2O is also swept into the
gullet. Excess water is pumped into contractile vacuole and then back into the external water.
Waste from the food vacuole is expelled via the anal pore.
Paramecium ingest food that is used in the respiration process in mitochondria, along with
oxygen to release energy for further metabolic processes = it is a HETEROTROPH. Oxygen
can diffuse over the plasma membrane and carbon dioxide diffuses out easily as the organism is
only 1 cell in size and the surface area is large enough to service the volume inside the
membrane.
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PLANTS AND THEIR REQUIREMENTS
Land/terrestrial plants require a constant supply of nutrients, water, CO2, O2, sunlight. All are
needed for growth & survival.
Plants are found in many different locations and survive/thrive so they must be well adapted to
the environment they are found in.
Plants fall into 2 groups, those that produce seeds/flowers(angiosperms) and those that don’t
produce seeds/flowers(gymnosperms) – such as ferns/mosses/pines.
Angiosperms = enclosed ovule or seeds(in the fruits and flowers). These developed from the
gymnosperms many millions of yrs ago.
Gymnosperms = naked ovules or seeds(in the form of cones or spores etc on the back of
leaves)
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PLANT STRUCTURE
All vascular plants have the same basic structure.
The shoot system, above the ground and root systems, below the ground are the main organs of
vascular plants.
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PLANT TISSUE
What is meristematic tissue and where are meristem cells found?
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What is meant by the word ‘differentiation’ of cells?
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List the 3 primary tissue types of plants and give a brief description of each.
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Vascular tissue is made up of what 2 main structures?
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Construct a table to compare the structure and function of xylem and phloem cells
Xylem
phloem
The connection between xylem and phloem cells
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When xylem cells die they create hollow tubes, arranged end to end, that act like straws to
allow the movement of water from the roots through the plant. They also act as the main
structural support for larger/taller plants like trees.
Phloem tissue has 2 types. List the 2 types and describe the function of each. Use the above
diagrams to help.
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WATER TRANSPORT SYSTEM
THE ROOTS
Roots systems can be of two types a taproot or fibrous roots.
Tap roots taper to a very thin end. They are very long and travel vertically downwards in
search of water.
Fibrous systems comprise of a multitude of thin roots that don’t go very deep – usually smaller
plants, shrubs and grasses. These types of roots help prevent soil erosion by holding soil in
place.
Regardless of type, roots will have tiny root hairs on them that vastly increase the surface
area over which water can be absorbed into the root. Root hairs can increase the root surface
are by up to 100 – 130 times its original area.
 Root hairs are extensions of the epidermal cells and are very thin in nature. Found just
behind the root cap region and absorb water many times faster than roots further away
from the root cap.
 Vascular bundle is found running down centre of the root and also strengthens the root.
 Root cap is like a helmet that protects the end of the root as it grows through the soil.
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 Water enters the root hairs and then the root via osmosis, travels through the thick layer
of parenchyma cells and into the xylem.
 Root pressure ensures that water and minerals travel further up to the stem.
Root pressure = the force that moves H2O up the stem. If stem is cut, water will continue
to ooze out of the top for some time.
THE STEM
In dicotyledons, vascular bundles are
arranged in a ring around the edge of
the stem/trunk [= trees, shrubs . Veins
in leaf have a branching effect.]
In Monocotyledons, vascular bundles
scattered randomly in the stem
[= grasses, lillies. Veins in leaves
usually run parallel down length of
leaf blades]
(See diagrams on page 93)
How does water actually move up the stem?
 Water molecules are attracted/stuck to each other by COHESION forces.
 The forces of attraction between water molecules and the molecules that make a
container, in this case, the xylem vessels are called ADHESION forces.
 The narrower the container/vessel, higher up the water reaches.
 The root pressure on the water decreases the higher up the plant/tree you get, so the
forces of adhesion/cohesion are responsible for the mvt of H2O up the stem.
 There is a continuos column of H2O from root to tip of the plant, this is called a
transpiration stream and the evaporation of water from the leaves of a plant, through
the stomata is called the process of transpiration. Transpiration is the reason water
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moves up the stem as the evaporation of water reduced the concentration of water in the
leaves and water will move via osmosis from high to low concentration.
 It is like a long water molecule chain being dragged through the plant from root, through
stem and leaf then out the stomata.
THE LEAF – STRUCTURE
leaf structure.htm
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(Biology Ch 4)
Student activity- Using your text, summarise the functions of the following in plants.
 Stomata
 Palisade cells (palisade mesophyll)
 Spongy mesophyll
 Epidermis
 Guard cells
1. Sometimes, dust and dirt can be blown onto the leaf and block the stomatal pores. Predict
what would happen to the rate of transpiration and photosynthesis. (Hint: what are the
compounds needed for photosynthesis and how does the plant obtain them, why does
water move through the plant?)
2. If you wanted to test your idea, how would you do this and what factors would you need
to control?