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Science in Action 7
Unit B – Plants for Food and Fibre
1.0 Understanding structures and life processes of plants helps us to interpret their needs.
- All seed plants have the same basic structures.
Ex) cactus and pine tree.
1.1 The Body of Seed Plants
Seed Plants – those plants that make seeds.
- come in all shapes and sizes.
- have the same structures, which do the same job in all plants.
- structures:
Flowers – each flower usually has both male and female parts for reproduction.
Stems – provide a pathway for movement of water and food.
- support the leaves and reproductive structures.
Seeds – contain an embryo that will form a new plant.
- contain a food supply for the embryo.
Leaves – produce food for the plant.
- take in and release oxygen and carbon dioxide.
- allow water to exit the plant.
Cones – there are separate male and female cones for reproduction.
Roots – absorb water and dissolved nutrients.
- anchor the plant in the soil.
1.2 Plant Processes
A Process for Moving Water Up from the Roots
- Plants move water from the roots up to the leaves through several processes.
Transpiration – the plant process that pulls the water up from the roots.
1st - evaporation of water from the surface of the leaves.
2nd – evaporated water pulls water inside stem up to the leaves.
3rd – water is continuously pulled which brings water into the roots.
Capillary Action - movement of liquid up a narrow tube.
Two processes help move the water up the narrow tube.
Cohesion – water is attracted to other water particles.
Adhesion – water is attracted to the walls of the narrow tube in stem.
In a very narrow tube the force of adhesion and cohesion is more attractive than
the force of gravity, which allows the water to move up through the stem.
Osmosis – in cells, the movement of water across the cell membrane.
- moves water into roots from the soil.
- water naturally moves:
High Water
Low Water
Concentration
→
Concentration
(in the soil)
(in the roots)
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A Process to Make Food
Photosynthesis – process by which plants use light energy, carbon dioxide, and
water to make their own food.
Chloroplasts – the structure in plants cells that carry out photosynthesis.
Equation
Solar + Carbon
Energy
Dioxide
→
+ Water
Food
+ Oxygen + Water
A Process to Use Food
Cellular Respiration – the process in which cells break down sugar particles into
carbon dioxide, water, and energy.
Mitochondria – the structure in plant & animal cells that carry out cellular
respiration.
Equation
Food
+ Oxygen
+
Water
→
Energy +
Carbon + Water
Dioxide
Processes to Move Substances In and Out of Plant Cells
- After making the food, the plants must transport it to the other cells.
Pores – tiny openings in the cell membrane of plant cells.
- acts like a filter, allow certain substances to move in and out of the cell.
- 2 important processes to move substances.
1) Diffusion – the movement of particles from an area of high concentration to an
area with a low concentration.
Concentration – the number of particles of one substance in a certain volume of
another substance.
2) Active Transport – the process in which large particles cross the cell
membrane; active transport requires energy.
Diffusion
- Can be seen in all substances.
- Substances move from HIGH → LOW concentrations
Osmosis
- Is basically the diffusion of water
- Very common in cells because water is small enough to move through pores.
A Process to Exchange Gases
Gas Exchange – the process by which carbon dioxide and oxygen move in and
out of the plant.
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1.3 Reproduction of Seed Plants
Life Cycle – the stages that an organism passes through in going from one
generation to the next.
Seed → starts → Seedling → grows & develops → Adult → pollination → Seed
to
reproductive
grow
structures
The Seed Stage
- A seed has 3 main parts
(i)
embryo
(ii)
stored food – used to nourish embryo until able to survive on own.
(iii) seed coat
The Seedling Stage
- Grows very fast.
- Produces own food through photosynthesis and nutrients from soil.
The Adult Stage
- Produces reproductive structures
Ex) flower or cone
Reproduction of Seed Plants
Pollination – process in which male and female parts of a plant join to produce a seed.
- Male part is called the pollen.
Pollen – small, sticky cells
- a plant produces millions of pollen grains
- Female part is called ovary.
Ovary – usually in the centre of the blossom.
- contains an ovule
st
1 Occurs after a pollen gain lands on the stigma of a flower, above the ovary.
2nd Pollen grain produces a pollen tube that grows down to the ovule.
3rd Pollen grains then transfer to the ovule and grow into a seed.
- Cone-bearing plants (conifers) usually have separate male and female cones
Male – produce pollen
Female – produce ovules (once pollinated seed develops on female cones)
- Many plants such as conifers & wheat fields, are pollinated by wind.
Pollinators – organisms that carry pollen from one flower to another.
1st the organism lands on a flower in search of nectar.
2nd pollen gets stuck to the body of the organism.
3rd then the organism transports the pollen to the next flower.
- Although it is done naturally, farmers develop ways to ensure it happens.
Ex) beehives near their plants
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Reproduction without Seeds
Vegetative Reproduction – reproduction of seed plants that does not involve the
production of seeds.
- these reproduced plants are genetically identical.
Examples
(i)
Some plants reproduce from stems
(ii)
Runners – long stems that grow along the soil of the surface and produce
new plants.
(iii) Rhizomes – stems that form underground stems and produce new plants.
(iv)
Bulbs, tubers, & corms – underground stems produced close to the plants.
(v)
Suckers – new plants that are produced from the roots of the parent plant.
- Common in the horticultural industry; new plants are produced in nurseries.
Technology to Reproduce Plants
Cuttings – a cut piece of a plant that is used to reproduce that plant.
- cuttings usually have a part of the stem and a few leaves.
Grafting – a technology to reproduce plants that involves attaching part of one
plant to a second plant.
1.4 Plant Structures are Adapted to Their Environment
-
Orange trees can not grow in Alberta, but white pine trees can.
Plants have structures and adaptations that match their environment?
Examples
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
Cacti in Dry environments
- have think stems to conserve water
- have tiny spines for protection
Grass
- thin leaves so many can fir in a small place for easy pollination.
- depth of roots help find water in drought conditions.
Sunflower
- have large, wide leaves to capture lots of sun.
Pretty Flowers
- have bright colours and sweet nectar to attract insects.
White Spruce Trees
- have thin needle-like leaves with thick resin coating to protect from
drying out.
Some plants
- have fibrous thick mat of roots to gather water near upper layers of soil.
- have long taproot that collect water that is deep in the soil.
Wild Mustard
- have adapted to produce seeds in a short growing season.
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1.5 Plant Needs and Growing Conditions
-
Plants need the right amount of:
- Light
- Water
- Nutrients
- Space
Plants need different amounts of Light
Ex) A fern needs less light than a marigold does.
Plants need different amounts of Water
Ex) A cactus needs very little water.
A rice plant needs to grow in water.
Plants need different Nutrients
Nutrients – are substances that provide the energy and materials that plants need
to grow. The main nutrients are:
- nitrogen
- phosphorous
- potassium
- calcium
- magnesium
- Plants need sufficient amounts of each nutrient to grow and develop properly.
Ex) Lack of nitrogen leads to yellow leaves
Plants need different amounts of Space
Ex) Buttercup plants need very little space compared to redwoods.
** Understanding a plants needs is an important tool to maximise a plants growth.
2.0 Plants play an essential role in the environment and in meeting human needs.
- Plants are important for human life on earth.
2.1 The Role of Plants in the Environment
- Plants have an important effect on the environment.
Examples
(i)
Plants provide Oxygen
Ex) produced by photosynthesis
(ii)
Plants provide Shelter
Ex) birds nest
(iii) Plants provide Food
Ex) produced by photosynthesis
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(iv)
(v)
Plants build and protect soil
Ex) decomposition builds soil
Prevents erosion – process that moves soil.
Plants are crucial for the Food Chain
Ex) Most common consumers are herbivores
2.2 We use Plants in Many Ways
-
Plants have an unlimited number of uses such as:
- Medicine (Ex) Paintbrush plant heals rheumatism
- Food (Ex) fruits & vegetables help keep us healthy
- Fibre (Ex) Shelter, Clothing, & Paper
- Other useful products (Ex) glue & rubber
2.3 Managing Living Resources
Living Resources – those living things that can be used to meet human needs.
- It is important to manage living resources to maintain healthy populations of
all the living things that make up those resources.
Changes Caused by Human Activity
1st Aboriginals used living resources for medicine, food, and fibre and so they
developed a close relationship with the living resources.
2nd Introduction of European tools allowed Aboriginals to be more efficient and
started to have a greater affect on the environment.
3rd European settlers started using living resources for themselves and others.
Which has led to great impacts, and a serious need to manage these resources.
Managing Living Resources for Now and the Future
Non- sustainable resources - In many places in the world humans are using living
resources more quickly than they are being replaced. This means they will not have
enough available in the future.
This has led to managing plans such as:
- Established methods and regulations.
Ex) What species can be harvested?
How they are to be removed?
How the forest is restored and replanted after harvesting?
This allows both industry and the living resources to co-exist.
3.0 Soil is an important resource that human activity can protect or degrade.
- Soil is a natural resource that is important to provide a healthy place for plants to
grow and many organisms to live.
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3.1 What is Soil?
- Soil is not just dirt. Soil has:
Minerals – pure, natural solid materials that are the building blocks of rock.
Organic Particles – particles that come from plants and animals that have died.
Humus – partly decomposed material from plants and animals that once lived.
Sandy Soil
- Is light brown
- Does not form clumps
- Mostly minerals, very little humus
- Dries quickly because water runs through it very fast.
Clay Soil
-
Feels slippery when moist.
Sticks together and can form a tight ball.
Dry clay is very had.
Colour can vary.
Lots of very small minerals, and little humus.
Fine texture.
Can hold lots of water, but little space for air.
Loam Soil
-
Crumbly, like a moist cake.
Dark brown or black.
Balance between organic particles and minerals.
Absorbs lots of water, and can stay moist for a long time.
Lots of nutrients, and is great for plants to grow.
** Each plant is adapted and grows the best in different types of soil.
3.2 Our Practices Can Improve or Degrade Soil
- Human harvesting techniques over time can remove the important nutrients from
the soil so future plants would not be able to grow well.
- Soil is an important natural resources.
Ex) animal food and shelter & human food and fibre
Fertilizer Use
- The lost nutrients in the soil can be replenished by fertilizers.
- 2 types of fertilizers.
1) Organic – made from sources such as animal or plant waste.
Ex) Animal manure or urea
2) Chemical – mixtures of types of chemicals that promote plant growth.
Ex) Potash (for potassium)
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-
The amount of fertilizer is important because too much and too little can be
harmful to either the plant or the environment.
Irrigation
- Is used to grow plants in dry areas.
- Ensures plants get the right amount of water at the right time.
- Must be carefully managed to promote optimal growth conditions.
Clearing the Land
- Before plants can be grown the land must be cleared:
- To prevent competition from other plants.
- Making it easier to plant seeds.
- Forest harvesters remove the desirable species and leave the rest, and then
replant young trees to keep the forest sustainable.
- Too much clearing can cause problems:
- Soil can be blown away by the wind.
- Pounding rain can compact the soil making it hard for new plants to
lay down roots.
- Clearing plants could take away shade, which keeps it cool and moist.
Plowing Changes Soil
- Plowing is the process of cutting into the soil and turning the top layer over,
which creates more air spaces and makes it less compact helping plants grow.
- Overtime plowing can damage the soil.
- Alberta farmers found that a top layer of stubble (trash cover) helps protect
the soil.
- An Albertan created the Noble Blade in the 1930s which allowed farmers
to plough under the surface thereby killing the weeds, but leaving stubble
on the surface. Today it is used around the world.
Crop Rotation Helps to Keep Soil Healthy
- Planting the same crop on the same soil year after year could lead to the soil
running out of important nutrients.
- Fertilizer can be expensive and hazardous to the environment.
Crop Rotation-practice of planting a different crop in a particular field each year.
- the crops that are rotated should be chosen based on their nutrient needs.
Ex) 1st plant should use lots of phosphorous, but little nitrogen.
2nd plant should use lots of nitrogen, but little phosphorous.
4.0 The ways that plants are gown and used are related to human needs, technology, and
the environment.
-
Human activities must focus on using sustainable practices to ensure the
environment does not collapse.
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4.1 Modifying Environments to Increase Yields
-
The human population is increasing every year, which means humans need
more plants to produce food and fibre to meet their needs.
Yield – the amount of useful plant material produced per plant, or per area
planted in a particular crop.
- Humans have developed many technologies to provide the best growing
conditions for plants, thereby increasing yields.
Ex) fertilizers
Shelter
Artificial Environments
(i)
Greenhouses – plants grown in controlled settings, with the appropriate
light, temperature, and nutrients to meet their needs.
(ii)
Hydroponic systems – plants grown in gravel or course sand, with a
continuous flow of nutrient-rich water pumped through.
4.2 New Plant Varieties are Developed by Selective Breeding
-
As time has gone by more and more types of certain vegetables have been
created to meet specific demands.
Ex) Carrots have been grown to:
- stay fresh in the store during the winter.
- develop in the short growing season of Alberta.
Species – living things of the same kind that are able to reproduce.
Variety – a group of organisms of the same species that has specific
characteristics that can distinguish it from other varieties of that species.
Traits – a characteristic of an organism.
- Humans produce plants with specific traits that we need or want.
Ex) Plants that can tolerate salty soil or colder climates.
Selective Breeding
Selective Breeding – a technology for producing new varieties of an organism
that involves choosing parents with desired traits in order to produce offspring with these
traits.
Ex) Farmers might notice certain plants grow taller, so they use their seeds
to grow their next years crop.
Genetic Engineering – process in which single genes are added to a plant’s
genetic material.
- the genes can come from other plants or totally different
living things.
Gene – tiny piece of material in a cell’s nucleus.
- each gene in a cell is responsible for the inheritance of certain traits or
characteristics.
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-
New varieties of plants can cause other problems like be more attractive to
insects, which could lead to the use of more herbicides (economic &
environmental costs)
Ex) Genetically engineered canola plants
4.3 Controlling Weeds and Pests
-
On Earth, some plants are considered useful and some harmful.
Plants that interfere with the growth of these crops are called weeds.
Ex) quack grass & smartweed
- Animals that eat or affect the growth of crops are called pests.
Ex) army cutworm larva
- Farmers must find a way to maximize crop yield.
I. Herbicides – a chemical that kills unwanted plants.
II. Pesticides – chemicals that are poisonous to insects.
- Possible Complications:
- Certain species of plants and insects could become immune.
- Certain useful plants and insects could be harmed.
- Could have environmental consequences.
III. Biological Control – a technology for controlling pest in which natural
predators of the pest are introduced to reduce their population size.
- Usually takes a long time.
- Not useful for large outbreaks.
4.4 Consequences of Environmental Management
Unintended Consequences – results of an action, not predicted or planned.
Environmental Management – the process of balancing the needs of humans
with the needs of the environment.
- Important to look at all possible consequences of human actions.
Monoculture – the practice of growing only one type of crop in a large area.
- Useful to cut down on cost and ferilizer use.
- Problems:
- Insect population explosion (large supply of food)
- Reduce biodiversity
Biodiversity – the number of different species in an environment.
- Our goal should be creating a sustainable environment.
Sustained – can be maintained or continued indefinitely.
- In any decision, economic and social effects should also be considered.
Economic – Crop rotation increases yields and consistency of poduction.
Social – Farm stability could ensure jobs for families.