plant behaviors how plants respond to external stimuli
TRANSCRIPT
Plant Behaviors
How Plants Respond to External Stimuli
Essential Standards
• 6.L.2 Understand the flow of energy through ecosystems and the responses of populations to the biotic and abiotic factors in their environment.
Clarifying Objectives
• 6.L.2.2 Explain how plants respond to external stimuli (including dormancy and forms of tropism) to enhance survival in an environment.
Essential Questions
• How do plants adapt to environmental conditions?
• Why do plants adapt to environmental conditions?
• What is dormancy?
• What are Tropisms?
Evolution of Plants
• Plants have evolved over thousands of years
• Plants now have the ability to grow TOWARDS vital resources like sunlight, water & nutrients
• This evolution of plants helps to ensure that they survive
Essential Questions
• Get with a partner and answer…
• Why do plants adapt to environmental conditions?
External Stimuli
• External Stimuli is anything in a plants environment that will cause it to physically react
• External Stimuli include– Temperature– Sunlight – Being Touched– Chemicals– Gravity – Water
Dormancy (Unfavorable Conditions)
• Dormancy is the other way plants respond to External Stimuli
• Dormancy is when a plant stops growing and reserves its energy for better conditions
• The plant or seed is not dying it is simply saving its growing power
Dormancy (Unfavorable Conditions)
• Dormancy happens when plants experience growing conditions in which they will be unsuccessful & die
• An example of this is flowers in the winter
• The seeds lie dormant in the winter and then come up when it gets warm again
Tropisms• Tropisms are the other way
plants respond to external stimuli
• Positive Tropisms are plant responses in the direction toward the External Stimulus
• Negative Tropisms are responses in the opposite direction of the External Stimulus
Tropisms
• Tropisms are advantageous to the plant because they support the organism well being
Essential Questions
• Get with a partner and answer…
• How do plants adapt to environmental conditions?
• What is dormancy?
• What are Tropisms?
Tropisms
• There are many different tropisms depending on what External Stimuli the plant is behaving towards
• Some examples of tropisms include① Phototropism/Heliotropism② Hydrotropism③ Geotropism/Gravitropism④ Thigmotropism⑤ Thermotropism
Phototropism (Sunlight)
• Phototropism is the plants response to light (sun)
• The plant will change direction and grow toward the sunlight
• Positive phototropism is when the plant begins adjusts itself to make sure it gets sunlight
Phototropism (Sunlight)
• Plants & trees will go to major lengths to make sure they get enough light
• Without light plants cannot go through photosynthesis
• This means that they will not be able to make their own food and will therefore die
Hydrotropism (Water)
• Hydrotropism is when plants respond to by their roots extending toward a lake or river
• Positive Tropism
• Hydrotropism occurs because a plant or tree is not getting enough water
Geotropism/Gravitropism• Geotropism & Gravitropism are
the same thing
• This is the plants response to gravity
• The plant will either want to grow upward toward the sky (positive)
• The plant might want to grow downward toward the ground (negative)
Thigmotropism (Touch)• Thigmotropism is a plants
reaction to touch
• It is a defense reaction to preserve its leaves
• Negative Tropism
• During Thigmotropism the plants leaves will quickly close up when they are touched
Thermotropism (Temp)
• Thermotropism is a plant or tree’s response to different temperatures
• When temperatures become cold during the night a plant will close its leaves to keep itself warm
• Thermotropism can be negative (cold) or positive (warmth)
• http://www.youtube.com/watch?v=VUWQFF0RJN4
EOG Questions
• A plant begins to bend when a tall building is built near it. Why does this occur?
• A) It is adjusting to changes in the temperature.
• B) It is growing away from the light source.
• C) It is adjusting to changes in the soil.
• D) It is growing toward the light source.
EOG Questions• Why do seeds go through a period of dormancy?
• A) It allows time for the right conditions to occur before the seed germinates.
• B) It allows time for dry soil to accumulate before the seed germinates.
• C) It allows time for sunlight to appear before the seed germinates.
• D) It allows time for pollination to occur before the seed germinates.
Important Points• Tropisms & dormancies are
evolutions of a plant meant to enhance survival
• External Stimuli from the plant’s environment influence the plant to make changes
• Dormancies are reactions by a plant or seed to unfavorable growing conditions
• Tropisms are reactions by the plant to its environment
• Positive Tropisms are movements by a plant toward the External Stimuli
• Negative Tropisms are movements away from the External Stimuli