Unit 7 ~ Learning Guide Name: INSTRUCTIONS Complete the following notes and questions as you work through the related lessons. You are required to have this package completed BEFORE you write your unit test. Do your best and ask questions about anything that you don't understand BEFORE you write the unit test. 7.1 NOTES: VACULAR PLANTS WITH SEEDS General Characteristics of Seed Plants There are two main groups of seed plants,. The in both. The advantage to having a seed is that the in comparison to those of the angiosperms. They are. The following structures are found in seed plants and are very important in their adaptation to living on land: 1. 2. 3. 4. 5. These structures and their functions will be the topics of the sections to follow. Page 1 of 15
Seeds The seeds. The within these seeds is. The seeds are diploid and. In Douglas-fir, the seed is filled with 60% lipids, 16% proteins, and 2% sugars, making it a high-energy and nutritious tissue. Roots Roots have three primary functions. First,. They are the principle water-absorbing organs of a plant. of the root and have greater contact with soil particles. Secondly,. This prevents it from blowing away or falling over. Finally,. This. Some roots may become specialized below-ground storage organs (example: carrot!). This storage of energy is an important strategy for surviving stress and dormancy. To the right is an image of the cross- section of a root.. Page 2 of 15
Roots grow by increasing in length through cell division. The root tip elongates and matures. The structures in the root cross-section include: 1. Epidermis (outer cells). 2. Cortex (loosely packed parenchyma cells). 3. Endodermis (inner cells). The endodermis contains a layer of a waterproof substance that stops further movement of water into cells. For water to get into the root it must pass through a selectively permeable membrane. The innermost tissues are vascular tissues that transport water, minerals and food. The outermost layer is the pericyle. Lateral roots are formed by the division of pericyle cells. Stems. They hold up leaves and flowers to the light. Stems also. For example, the cactus stores water and the sugar cane stores large amounts of sugar in their stems. The diagrams below illustrate how sugars made in the leaves move into the phloem and how water from the roots is moved up into the stem by xylem. Page 3 of 15
Leaves. Most leaves are thin and flat. Others are more needle like in appearance. Leaf Structure. Spongy mesophyll allows oxygen, carbon dioxide and water to diffuse in/out of the leaf. Notice the location of the stomata and guard cells in this diagram. Stomata two kidney- shaped. Stomata are. This opening and closing is regulated by the amount of water in the guard cells. When guard cells are full of water they swell, making them spread apart to create an opening. The necessary for photosynthesis can enter the leaf through the stomata and the produced by photosynthesis can pass out of the leaf through the same opening. is also lost in the process of transpiration, for example cottonwood trees lose 100 gallons of water on a hot day. Page 4 of 15
7.1 PRACTICE: VACULAR PLANTS WITH SEEDS 1. What is the primary function of a seed? (1 mark) 2. What are the proposed selective advantages of a seed over a spore? (2 marks) 3. Compare and contrast the seeds of gymnosperms and angiosperms. (3 marks) 4. What are the three key functions of roots? (3 marks) Page 5 of 15
5. What are the two key functions of stems? (2 marks) 6. What is the primary function of leaves? (1 mark) 7. Briefly describe the structure and function of stomata. (5 marks) Page 6 of 15
7.2 NOTES: GYMNOSPERMS Diversity of Gymnosperms Gymnosperms includes four divisions of plants: 1. 2. 3. 4. The Pinophyta or conifers are the most widely studied. They are the largest group and are the base of the. All conifers have no protecting ovary wall around the seed. In fact,. adaptations that allow them to live on land include; 1. Alternation of generations. 2. 3. Seeds contain fully formed plant embryo. 4. Gymnosperms can store food. 5. 6. 7. Contain Vascular tissue that allows plants to grow to great heights giving an advantage in the fight for sunlight. Here's an image of the vascular tissue within the trunk of a tree that moves water and nutrients. It is like a circulatory system for a tree. Page 7 of 15
Gymnosperm Divisions Cycads - Division Cycadophyta The cycads are than they are as a living species with most of the fossils dating to the time of the dinosaurs in the Mesozoic era. Most cycads resemble palms and are very slow growing. In cycads, are formed. Ginkgo - Division Ginkgophyta Ginkgo biloba is. There are male and female trees which could easily be mistaken for angiosperms. The trees have small flat leaves and produce seeds that look like fruit. However, like gymnosperms pollination is by wind and ciliated sperm swim from the pollen tube to the egg in the archegonium. They are but only the males are planted typically because the females have a pungent smell when they produce seed. Gnetophytes - Division Gnetophyta There are three groups within Gnetophyta and all three are fairly strange shrubs. They are the most closely related to angiosperms of all of the living gymnosperms and they even undergo double fertilization which is a defining characteristic of angiosperms. Conifers - Division Pinophyta Conifers received this name due to their. Well known conifers include the cone bearing. Their and don't bear much resemblance to leaves macroscopically which is why and most conifers retain their needles in winter and continue to photosynthesize with a reduction in activity. Page 8 of 15
Below is an image of pine needles. The needles are in bundles of two so it could be a lodgepole or jack pine. Life Cycle of Gymnosperms, as in other seed plants,. However, it is. The seed of a gymnosperm to keep it from drying out so that the embryo can survive long periods before growing.. When the seed lands on the ground it will grow into the dominant sporophyte tree. Once mature, this tree will bear male or female cones. On trees that have both male and female cones, the male cones are located on lower branches near the tips to avoid selffertilization. This allows the pollen (n) of the male cones to float to another tree on a windy day giving cross-fertilization. When a pollen grain lands on an ovule of a female cone (n),. There are two sperm produced by each pollen grain. One sperm eventually fertilizes the egg and the other degenerates. Once the egg is fertilized forming a zygote (2n), it will grow into a seed ready to become a new sporophyte tree. Page 9 of 15
Diagram of the Gymnosperm Life Cycle. Economic Importance In first world countries the primary woods used for construction are gymnosperms. The gymnosperms are known in the. The softwood lumber industry with most of the wood going to the USA. are all examples of conifers used around the world for. This is the primary economic importance of gymnosperms as most do not produce edible fruits or roots and the stem tissue is too woody for consumption. However, there are a few examples of gymnosperms that are consumed., due to its colour and hardiness, but its blossoms are also used for the production of gin. Many other gymnosperms are used in landscaping gardens but it is usually to provide a backdrop or contrast to the beauty of an angiosperm. Pine beetle infestations have been of particular concern to the logging industry in the past decade. Page 10 of 15
7.2 PRACTICE: GYMNOSPERMS 1. What does the term gymnosperm refer to? (1 mark) 2. Identify three adaptations that enable gymnosperms to live on land. Explain in your own words how these adaptation likely proved to be a selective advantage. (6 marks) Page 11 of 15
3. What is the dominant stage of the gymnosperm life cycle, and is this stage haploid or diploid? (2 marks) 4. Male pollen and the female ovule, both found in cones, are haploid. Why is this necessary/important? (2 marks) ~ END OF BIOLOGY 11 UNIT 7 LEARNING GUIDE ~ Page 12 of 15
UNIT 7 ANSWER KEY 7.1 PRACTICE: VACULAR PLANTS WITH SEEDS 1. What is the primary function of a seed? (1 mark) - the seed contains the embryo and allows for the plant to be dispersed either through falling and wind dispersal or more frequently by attaching to or being eaten by and dispersed by an animal 2. What are the proposed selective advantages of a seed over a spore? (2 marks) - a seed has stored food that allows embryo to better survive in nutrient lacking conditions - a seed provides physical protection - a seed can attract animals and thus, encourage dispersion of the plant 3. Compare and contrast the seeds of gymnosperms and angiosperms. (3 marks) - both provide embryo with nutrients and enhance dispersion however - gymnosperm = naked/uncovered seeds such as found on surface of scales that make up cones - angiosperm = covered seeds (fruit) found in flowering plants 4. What are the three key functions of roots? (3 marks) - uptake of water and minerals from soil (helps increase surface area) - anchor plant in soil - can store food (such as carrots) 5. What are the two key functions of stems? (2 marks) - improve height/exposure to sun - transport water, minerals and nutrients throughout plant 6. What is the primary function of leaves? (1 mark) - collect sunlight and perform gas exchange (CO 2 uptake and O 2 release) necessary for photosynthesis Page 13 of 15
7. Briefly describe the structure and function of stomata. (5 marks) - Pores/opening typically in epidermis of leaves that exchange gas (CO 2 uptake and O 2 release) - Stomata are surrounded by 2 kidney-shaped guard cells that can open and close to maximize gas exchange yet minimize water loss as needed 7.2 PRACTICE: GYMNOSPERMS 1. What does the term gymnosperm refer to? (1 mark) - naked seed 2. Identify three adaptations that enable gymnosperms to live on land. Explain in your own words how these adaptation likely proved to be a selective advantage. (6 marks) - Alternation of generation the sporophyte diploid stage and gametophyte haploid stage can generally withstand different environmental conditions, the ability to survive more environmental conditions generally means greater overall survival - seeds resist drying out allows seed to withstand periods of drought thus increasing chance of survival in a greater range of environments - seeds contain fully formed plant embryo can rapidly grow upon landing in an appropriate nutrient rich area the more quickly a plant establishes the greater chance for success - seeds can store food can survive longer periods of time if conditions are not ideal for growth - airborne pollen can disperse in dry windy conditions does not require water and thus, can have greater dispersal = better chance of encountering a better environment for growth and less competition - waxy cuticle prevents drying out (desiccation) = better chance of survival in drier conditions - contain vascular tissue = can grow in drier climates, can grow larger to access more light, better dispersion, more resistant to grazing 3. What is the dominant stage of the gymnosperm life cycle, and is this stage haploid or diploid? (2 marks) - Sporophyte (2n) = diploid Page 14 of 15
4. Male pollen and the female ovule, both found in cones, are haploid. Why is this necessary/important? (2 marks) - two haploid gametes (sperm and egg) come together to form a diploid gamete - egg (n) + sperm (n) gamete (2n) - if the gametes were not formed by meiosis where the chromosome numbers are halved from two copies to a single copy, each fertilization event would double the number of chromosomes in the organism (2n 4n 8n 16n ) unfortunately, more is not better and the organism would not survive Page 15 of 15