• What do these words have to do with science?

Cycles and Systems

•Cycles and Systems explore the constant processes that surround us. All of the Earth’s processes connect and work together. From the movement of rocks to the changing forms of water, we find that less than 100 elements and the Sun's energy are the keys to all living things.

Everything!

By Moira Whitehouse PhD.

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•In every discipline of science: biology, geology, astronomy, meteorology, physics and chemistry, we find that whatever functions are being performed they are frequently performed as part of some cycle in some system. When one part of a cycle fails or is removed, the cycle and the system fails.

•And here is a list of a few systems:

Moon and Earth, Solar system, galaxies, ecosystems, food web, all body systems, (skeletal, digestive, immune, etc)

•Here is a list of just a few cycles:

electrical circuit, bicycle, gas engine, rock cycle, water cycle, carbon cycle, nitrogen cycle, phosphorous cycle, cycle of sunspots, moon cycle, season cycle, Celoin cycle, Kreps cycle, food cycle, cycle of constructive and destructive forces.

First, let’s look at cycles. What is a cycle?• In general: Any complete round or series of occurrences that repeats or is repeated.• In science: An interval of time during which a characteristic, often regularly repeated event or sequence of events occurs:Sunspots increase and decrease in intensity in an 11-year cycle• In science: A single complete execution of a periodically repeated phenomenon:

A year constitutes a cycle of the seasons.

• In science: A periodically repeated sequence of events:

The cycle of birth, growth, and death

Next, we’ll look at systems. What is a system?

• In general: A combination of components that act together to perform a function not possible with any of the individual parts .

the nervous system; the skeletal system

• In biology: A group of physiologically or anatomically complementary organs or parts:

• In astronomy : a number of heavenly bodies associated and acting together according to certain natural laws:

the solar system;

•As we go through these few cycles and systems, remember that this hardly touches the surface...

•but it does cover some of the major ones that fifth grade students should be familiar with.•In this order, we will look at:

•Life cycle of a plant (this presentation)

•The water cycle (a separate slide show)

•The nitrogen and carbon cycles (a separate slide show)

Life cycle of a Plant

•The world of plants is large and complex.

•We will study only a small part, the life cycles of angiosperms (flowering plants).

•The plant kingdom, however, includes many other types of plants whose life cycles will be very different the ones we will study.

•Here is a quick overview of the plant Kingdom:I. Bryophytes: Small with leaflike, stemlike,

and rootlike structures. Reproduce by spores: mosses, liverworts, hornworts.

II. Vascular Plants: Larger with true leaves, stems, and roots.

B. Seed Plants: 1. Gymnosperms: Usually have cones,

no flowers, seeds not enclosed in fruit: pines, spruces, firs, hemlocks, cycads, ginkgo.

A. Seedless: Reproduce by spores. Ferns, horsetails, club mosses.

B. Seed Plants: 1. Gymnosperms: Usually have cones,

no flowers, seeds not enclosed in fruit: pines, spruces, firs, hemlocks, cycads, ginkgo. 2. Angiosperms: Have flowers, seeds enclosed in fruit.

Our aim in this section is to deepen our understanding of the life cycle of flowering plants, the angiosperms.Most of us have a pretty good understanding of the basic stages of the flowering plant’s life cycle, but at the nitty-gritty level, things can become complex.

As you may remember the life cycle of a flowering plant fits into the following stages:

•Germination of the seed•Seedling•Mature plant

•Development of the fruit

•Flowering

•Fertilization

•Seed dispersal

As the following four processes are crucial to plant survival, we examine each one.

•transpiration

•fertilization

•respiration

•photosynthesis--the process of metabolizing (burning) glucose to yield energy for growth, reproduction and other life processes.

—the process by which the chlorophyll in plants captures light energy which is then used to convert carbon dioxide and water into a simple sugar called glucose.

--the loss of water vapor through the stomata of leaves.--The joining of a male

and female cell.

photosynthesis

—the process by which the chlorophyll in plants captures light energy which is then used to convert carbon dioxide and water into a simple sugar called glucose.

Let’s talk about each of these.

During photosynthesis, the leaves of a plant take in carbon dioxide from the air and receive water from the soil. Using light energy, the plant changes these ingredients into a simple sugar called glucose.

--cross section of a leaf, where all this magic work takes place.

http://openlearn.open.ac.uk/ Creative commons attribution image

The chemical equation for the chemical change involved photosynthesis is:6CO2 + 6H20 = C6H12O6 + 6O2

carbon dioxide water glucose oxygen

Light energy provides the energy for this chemical reaction.

Light energy

Plant cells have cell structures called chloroplasts which contain chlorophyll, a green substance that absorbs light energy. Chlorophyll is what gives plant leaves their green color.

http://www.micrographia.com/Images free for nonprofit use

Only plants can produce food though photosynthesis. Animals cannot make their own food. However, both plant and animals cells respire— “burn” glucose in order to secure energy to carry out their life processes. In plants that process is called “respiration”.

Respiration

--the process of metabolizing (burning) glucose to yield energy for growth, reproduction and other life processes.

Remember, photosynthesis produces glucose and now we will see how that glucose is used by the plant (through respiration) to get immediate energy for growth, reproduction and to absorb nutrients, etc.

Notice that the equation for respiration is the opposite of photosynthesis:

C6H12O6 + 6O2 = 6CO2 + 6H20 + energy

In respiration, to grow and carry out its life processes, a plant “burns” glucose. During this process, the glucose produced in photosynthesis combines with oxygen. This chemical change results in the release of carbon dioxide, water vapor and energy.

1. For storing food in seeds and roots. Before winter, some plants stores starch in their roots so they can survive the winter and start growing again quickly in the spring. Fats and oils are stored in seeds to use for germination.

A plant changes some of the glucose it manufactures into substances such as starch, fats, and oils.

It uses these substances for two things.

2. To build plant tissues such as leaves, wood, flowers, fruit and roots.

http://ecosys.cfl.scf.rncan.gc.ca/Images for use by public noncommerical use by Natural Resources Canada

Here we can see the two processes—photosynthesis and respiration occurring in a leaf.

The undersurface of leaves have holes called stomata. This is where carbon dioxide and oxygen from the air enter the plant. It is also through these same holes that carbon dioxide, oxygen and water vapor are released.

http://www.micrographia.com/Free images for nonprofit use

Image from Enchanted Learning

Water vapor

Water vapor

Carbon dioxide

Carbon dioxide and oxygen

Oxygen

WaterOxygen

Plants take up the oxygen they need through their their leavesand through their roots

Plants, animals and most microorganisms need oxygen for respiration.

This is why for plants and microorganisms too much water is deadly.

And we just saw that some of that oxygen comes from the soil.

Overly wet or saturated soils are detrimental to both root growth and function, and to the decomposition processes carried out by microorganisms in the soil.

Water fills the spaces in the soil forcing the oxygen out.

Comparison of Photosynthesis & Respiration

Photosynthesis Respiration

Produces sugars from energy Burns sugars for energy Energy is stored Energy is releasedOccurs only in cells with Occurs in most cells chloroplastsOxygen is produced Oxygen is usedWater is used Water is producedCarbon dioxide is used Carbon dioxide producedRequires light Occurs in both dark and

light

transpiration

--the loss of water vapor through the stomata of leaves

Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere.

http://ga.water.usgs.gov/

Transpiration serves three purposes:

1. Movement of minerals up from the root (in the xylem) and sugars (products of photosynthesis) throughout the plant (in the phloem). Water serves as both the solvent and the avenue of transport.

2. Cooling of the plant.

3. Turgor pressure. Water maintains pressure in cells much like air inflates a balloon, giving the non-woody plant parts form. Turgidity is important so the plant can remain stiff and upright and get to the light. It also is the force that pushes roots through soil.

Carbon dioxide is absorbed through the stomata (holes in the leaves) and water vapor and oxygen are given off.

Image from NASA

Fertilization

The joining of a male and female cell.

To understanding fertilization in a flowering plant will need to look at the parts of a flower..

The pistil is made up of three parts: stigma, style and ovary. The stigma is the sticky knob at the top of the pistil. The style is the stem that holds up the stigma and is attached to the ovary which contains the female egg cells called ovules. .

The female part of the flower is the pistil which is usually in the center of the flower.

A stamen is made up two parts:

The male parts of the flower are called stamen. They usually surround the pistil.

1. the anther at the top of the stamen which contains pollen (the male reproductive cells) and

2. the filament which supports the anther.

Petals are also important parts of the flower, because they help attract pollinators such as bees, butterflies and bats.

There are tiny green leaf-like parts called sepals at the base of the flower. They help to protect the developing bud.

During the process of fertilization, pollen lands on the stigma and a tube grows down the style and enters the ovary.

The male reproductive cells travel down the tube and join with the ovules, fertilizing them.

Each fertilized ovule develops into a seed and the ovary becomes the fruit.

The fruit is the ripened ovary of a plant containing the seeds. After fertilization, the ovary swells and becomes the fruit. Fruits may be fleshy fruits, seed pods, or shells. Many things we all call vegetables are really fruits such as tomatoes, cucumbers and beans.

Wikipedia commons

In order for fertilization to take place, the flower must be pollinated. Something has to carry the pollen from the stamen to the pistil usually of another flower.

Birds, bats and insects such as bees are common pollinators.

http://www.flickr.com ktjypryn http://www.flickr.com sharon, MA

Another way plants are pollinated is by the wind. Grasses such as wheat, oats, barley and corn are pollinated by the wind.

Flowers such as those of an oak tree, wheat, and corn are pollinated by wind.

Male tassels, female silks of a corn plant

Stamens of a wheat flower

Flower of an oak tree

Bean seed

Part of every seed is a tiny plant (embryo) with leaves, stems and root parts waiting for the right condition to germinate. The seed also contains a short-term supply of stored food called the endosperm. It is used by the embryo for growth until the seedling can make its own food.

Part of every seed is a tiny plant (embryo) with leaves, stems and root parts waiting for the right condition to germinate.

The right conditions, of course will involve there being some water there as well.

Which brings us to our next subject, water and the

Water Cycle