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Plant Adaptations for Survival 6-2.4 Summarize the basic functions of the structures of a flowering plant for defense, survival, and reproduction. 6-2.8 Explain how plants respond to external stimuli (including dormancy and the forms of tropism known as phototropism, gravitropism, hydrotropism, and thigmotropism). 6-2.9 Explain how disease-causing fungi can affect plants Structures for Defense in Plants Plants have structures for defense that protect them from outside threats. Without these defenses, the plant might be harmed or could die. 5 Examples of Natural Defenses: Thorns, Poisons, Plant Structures, Dormancy, Tropisms 1. Thorns Plants use thorns to deter animals from either eating the plant or getting too close to it. 2. Poisons Chemicals found in some plant leaves, fruit, or seeds can cause an animal that eats it to die, be sick, or cause irritation. Poisonous plants are sometimes brightly colored to advertise that it is harmful 3. Plant Structures for Survival Plants have structures that allow them to survive in their habitats when the conditions are not suitable. The 4 structures that help a plant survive: Leaves, Stems, Roots, Seeds □Leaves Location of photosynthesis, respiration, and transpiration - In some plants (like succulents) they also store water for the plant. - Plants with a waxy cuticle are better adapted to keep the water in the leaf. □Stems Main support for the plant. It holds up the leaves toward the sun for photosynthesis to occur. Contains vascular tubes (xylem, phloem) for transportation of water and food. Serves as a food storage location. Different plants have stems that are best adapted to their environments. □Roots The larger the plant, the bigger the root system has to be. Root Hairs Taproot Extend from roots, increase water Act as anchors absorption to hold the plant in the soil. Ex: Dicots (carrots, dandelion, cacti) Fibrous Root Increase surface area to absorb more water and nutrients. Ex: Monocots (grass, corn, some trees) □Plant Adaptations for Dry climates -spines instead of leaves -small surface area minimizes evaporation -stems that can store water -widespread root system for finding water 4. Dormancy □Seed Dormancy - The ability of a plant or seed to shut down to survive periods where the plant may die is called dormancy. - Dormancy in seeds is helped by the seed coat which protects the embryo from drying out and from physical damage during the period of shut down. - Dormancy ends when conditions are more suitable for the seedling to survive. □Leaf and Branch Dormancy - Dormancy in plants causes leaf and branch loss during periods of poor growing conditions. - Leaves return when there is no danger of poor growing conditions. Ex: How does losing its leaves in the winter help a tree survive? 5. Tropisms Tropisms are a natural tendency for a plant to respond toward or away from a stimulus Are caused by hormones inside the plant cells Examples: Thigmotropism, Hydrotropism, Phototropism, Gravitropism (geotropism) Thigmotropism ▪ Growing or response to touch ▪ Adaptation to protect themselves from possible harm or obtain resources. Hydrotropism ▪ Tendency of a plant to move towards or away from water. ▪ The ability of a plant to seek out water sources ensures the plants survival. ▪ Best evidence is when growth toward water is stronger than gravitropism. Phototropism ▪ Ability of a plant to bend towards or away from light. ▪ If it is in the shade, it is possible for a plant to bend around the shade to find the sun. Gravitropism ▪Also known as Geotropism ▪Ability of a plant’s stem to grow against gravity and the roots to grow with gravity. ▪Its role is important because germination usually occurs in the dark, underground. Which type of root are the following pictures? Fibrous or Taproot? 1. __________________________ 2. ___________________________ 3. ____________________________ 4. How long does adaptation usually take? A. a decade B. an hour C. a few days D. centuries 5. What does it mean when a plant adapts? A. It grows on the rainforest floor or under water C. It grows giant leaves, and has very bright flowers B. It changes itself to fit in better with its environment D. It converts its surroundings into a kinder climate 6. Why do some plants in the rainforest have bright flowers and grow close to the ground? A. To repel any extra rainfall C. To keep animals and people away from them B. To get as much sunlight on their leaves as possible D. To attract birds, and insects for pollination 7. How have some rainforest plants adapted to receive enough sunlight? A. By growing poisonous flowers C. By growing giant, bright flowers B. By growing giant, slippery leaves D. By growing long, deep roots 8. What are the two main types of roots? 9. What covers the leaves of succulents to protect them from water loss? A. chlorophyll C. poison B. cuticle D. stomata Stimulus Light Water Gravity Touch Tropism Response 10. 11. 12. 13. 14. Gravitropism occurs because seeds do not need _________________________ to germinate; therefore, the stems and root must rely on gravity to direct them. 15. Plants have reproductive adaptations. Which of the following would be an adaptation for seed dispersal by wind? A. apple seed C. onion seed B. dandelion seed D. strawberry seed 16. Why would a root produce root hairs off of it? 17. Which root system is better adapted to absorb water and why? 18. What tropism would an ivy plant require to grow to full size? Fungi Belong to the Kingdom of Fungi Are heterotrophs Absorb nutrients from the living or dead organisms they grow on Many grow in or on other organisms Mold: often grows on old food Mushrooms: often grows on trees Disease-Causing Fungi Can eventually kill the plant it infects Can cause losses in food crops Disease-Causing Fungi Examples – Grain mold, Wheat rust, Corn smut – Diseases also affect rice, cotton, rye, and soybeans Helpful Fungi Helpful as decomposers – breaks down decaying matter Can be made into medicines – Penicillin fights bacteria Are food – Mushrooms, truffles 19. True or False: Fungi do not make their own food. 20. How does fungi get the food that it eats? 21. Why are some disease-causing fungi dangerous for plants? 22. True or False: All fungi are bad or dangerous.