Agenda 10/29 Practice FRQ Plant Adaptations Transpiration fake lab Turn in: Chapter 39 Notes, video notes Homework 1. Plant Hormone Experiments (on website)

Design an Experiment FRQ Outlines Anytime you are asked to design an experiment on an FRQ question you must include: Independent variable- Dependent variable- Hypothesis/Prediction- Control Group- Experimental Group- Constants- Method for Collecting Data- Quality Control/Multiple Trials- Statistical Tools-

Homeostasis and Water Balance Trees that experience a prolonged drought may compensate by losing part of their crown as a consequence of leaves dying and being shed. Resources may be reallocated so that more energy is expended for root growth in the “search” for additional water. Ask students the following question: What evolutionary role do plants surviving drought conditions play? (The surviving plants may have adaptations that contributed to their survival. These adaptations may be passed on to future generations allowing them to thrive in more arid environments.)

Natural Selection and Arid Environments Ask students to come up with examples of plant adaptations to arid environments before moving on to the next slide.

Natural Selection and Arid Environments Plants that have adapted to arid environments have the following leaf adaptations: Leaves that are thick and hard with few stomata placed only on the underside of the leaf Leaves covered with trichomes (hairs) which reflect more light thus reducing the rate of transpiration Leaves with stomata located in surface pits which increases water tension and reduces the rate of transpiration Leaves that are spine-like with stems that carry out photosynthesis (cacti) and store water. Be sure to connect natural selection to being in arid environments and adaptations. Ask students to work in small groups and come up with these connections.

Natural Selection and Flooding Plants that experience prolonged flooding will have problems. Roots underwater cannot obtain the oxygen needed for cell respiration and ATP synthesis. As a result, leaves may dry out causing the plant to die. Additionally, production of hormones that promote root synthesis are suppressed. Ask them to explain how occasional flooding might select for plants that can live in an area where there is standing water such as swampland. (The plants that survive flooding may have some adaptations that have helped them survive. These adaptations are passed on to future generations so they are better adapted to life in a wetter environment.)

Adaptations to Water Environments Again ask students to come up with adaptations before moving to the next slide.

Adaptations to Water Environments Plants that have adapted to wet environments have the following adaptations: Formation of large lenticels (pores) on the stem. Formation of adventitious roots above the water that increase gas exchange. Formation of stomata only on the surface of the leaf (water lilies). Formation of a layer of air-filled channels called aerenchyma for gas exchange which moves gases between the plant above the water and the submerged tissues. Connect the adaptations and wet environment to natural selection.

Nutritional Adaptations in Plants Epiphytes- grow on other plants, but do not harm their host Parasitic Plants-absorb water, minerals, and sugars from their host Carnivorous Plants- photosynthetic but supplement their mineral diet with insects and small animals; found in nitrogen poor soils

Halophytes: Plants adapted to high salt environments Plants adapted to salt water environments. “Halophyte” means “salt plant” Ask how plants exposed to occasional salt water and survive might be involved in natural selection. (The plants that survive a saline environment may have some adaptations that have helped them survive. This may be passed on to future generations so that they may live in a more saline environment.)

Adaptations of Plants: Saline Environments Soil salinity around the world is increasing. Many plants are killed by too much salt in the soil. Some plants are adapted to growing in saline conditions (halophytes) Have spongy leaves with water stored that dilutes salt in the roots Actively transport the salt out of the roots or block the salt so that it cannot enter the roots Produce high concentrations of organic molecules in the roots to alter the water potential gradient of the roots

Transpiration Lab Materials: plants, scales, water, saran wrap Plants were massed initially, and then placed in a specific environment. Over a week, the plants were weighed each day. I’ve provided that data for you.

Whole Plant Transpiration Data Transpiration Lab Control Fridge Freezer Dark Light Fan Day 1 190.2 g 269.8 g 231.6 g 248.4 g 304 g 208.7 g Day 2 179.2 266.1 149.6 253.3 283.6 190.6 Day 3 148.4 168.3 228.7 246.2 250.6 110.5 Day 4 134.5 262.2 141.6 240.1 144.7 98.7