Forces in Everyday Life http://leavingbio. net/Plant%20Responses Forces in Everyday Life http://leavingbio.net/Plant%20Responses.htm Homework Exercise 4 Use the link and notes to complete a frame on Tropisms

Forces in Everyday Life External Environmental Factors   Light- Light, obviously affects the plants ability to grow because light is needed for photosynthesis. Through photosynthesis the plant makes its energy carrying molecules. It is also needed for the production of chlorophyll. Day Length- Day length causes the plants to flower. Many other roles of day length are being studied such as fruit and seed germination, dormancy, and leaf loss. Gravity- Gravity causes roots to grow down toward the soil and roots to grow up away from the source of gravity. Temperature- Higher temperature, to a point, is best for plant growth while low temperatures are needed for some plants to flower.

Forces in Everyday Life 1. Tropism: the way a plant grows in response to stimuli in the environment. Tropisms are usually named for the stimulus involved and may be either positive (towards the stimulus) or negative (away from the stimulus). Phototropism: growth response to light -Plants bend towards light Geotrophism: growth response to gravity -plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil. Thigmotropism: growth response to touch -vines grow up around trees, venus flytrap closes when leaves are touched Hydrotropism: is the growth response of a plant to water.

Forces in Everyday Life Phototropism: growth response to light -Plants bend towards light

Forces in Everyday Life Geotrophism: growth response to gravity -plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil. Roots exhibit positive geotropism while stems and leaves exhibit negative geotropism.

Forces in Everyday Life Thigmotrophism: growth response to touch -is the growth response of a plant to physical contact (touch). Plants that cling to physical structures such as walls exhibit positive thigmotropism.

Forces in Everyday Life Hydrotropism: is the growth response of a plant to water. Roots exhibit positive hydrotropism.

Forces in Everyday Life Seedlings push upwards against gravity. Their root tips are shaped like a wedge to push down into the soil as they grow.

Osmosis Turgor Pressure causes the cell to expand Osmosis is diffusion of water through a differentially permeable membrane from a region where there is more water, to a region where there is less. Turgor Pressure causes the cell to expand

Forces in Everyday Life Plants need water to maintain turgor pressure, which helps to keep them erect. The leaves of this plant are droopy because of a lack of water. Turgor Pressure is a force exerted outward on a plant cell wall by the water contained in the cell vacuole. http://www.youtube.com/watch?v=fNyYuVarTIQ

Molecular Movement Plasmolysis - (Dehydration in Plants) Loss of water through osmosis is accompanied by shrinkage of the cell membrane away from the cell wall.

Plasmolysis (Dehydration)

Turgor Pressure A lot of turgor pressure Less turgor pressure

Substances Transported by Active Transport How do plants manage to survive growing in salt water? Obtain water via osmosis Cells contain organic compounds that prevent plasmolysis (dehydration) Salt is pumped out of the cells by active transport Active Transport - when cells must move materials in an opposite direction. (like salt) Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display

Forces in Everyday Life Your body has many different types of simple machines Most machines in your body are levers that consist of bones and muscles. The muscles produce the input force, and the output force is sued for everything from lifting your hand to swinging a hammer. A muscle can't push, only pull. How can you bend your arm? Class three lever (crane)

Forces in Everyday Life Your body has many different types of simple machines

Forces in Everyday Life What happens if you increase pressure on a fluid at one end of a container with a hole at the other end? This example shows how a force pump works. A force pump causes a fluid to move from one place to another by increasing pressure in the fluid. Your heart is a force pump. Blood is the fluid.

Forces in Everyday Life If our incisors are good for cutting, why don’t we use them to chew? (it’s not efficient, because cutting only breaks the food into two pieces, the molars can mash the food without breaking the pieces apart).