Transcript Plants
Plants Chapters 22-25 What is a Plant? Eukaryotic organism Multicellular Autotrophic Chloroplast Plants have chloroplast that carry out Photosynthesis Photosynthesis (uses sunlight as energy sourche): CO2 + H20 -> Glucose (C6H12O6) and O2 Chloroplast are green pigment that reflects green light Has internal membrane that increases surface area What is the advantage to Photosynthesis/Autotroph: Can make own food don’t need to hunt of find Plant cells have cell walls to add rigidity and protect the cell The cell walls are made of cellulose which we cannot digest Cellulose is a Carbohydrate Plant types Mosses • They lack a vascular system and true roots • Low growing plants that like to live near a water supply • These evolved fistswhy they are most primitive Ferns • Have roots and a vascular system • Do not have seeds Roots The usually underground portion of a plant that lacks leaves serves as support draws minerals and water from the surrounding soil sometimes stores food Root hairs- provide increase surface area Roots are specialized for Mitosis why? What is vascular tissue? Tissue in the plant that transports water and nutrients • Xylem – transports water • Phloem – transports nutrients • Transpiration – water flows through the plant from root to leaf Released onto leaf undersurface through stomata and evaporates How are roots and vascular tissue an adaptation: allow plant to live in more arid conditions Grow to taller heights because can move water and nutrient by means other then diffusion Gymnosperms Cone bearers • Seeds are exposed • Called evergreens or conifers • Remain green all year- why is this an advantage? Can perform photosynthesis all year Seeds A fertilized plant ovule containing an embryo. Why is this an adaptation: sexual reproduction -> increased genetic variation Germination •Process by which plants emerge from seeds and begin growth •Can lay dormant for long periods and wait on proper conditions •Temperature •Water Why is this advantageous? •Best chance for survival Pine Needles The long, slender shape reduces leaf area, which, in turn, reduces the amount of water vapor escaping the leaf. (one time less surface are is an adaptation) Pine needles are shed year round – just not all at one time. Angiosperms Flowering plants • Seeds protected by a layer of tissue • Flowers are the reproductive organs • Ovaries surround and protect seed inside the flower • Many times the ovaries will develop into fruit Flowers known as a bloom or blossom is the reproductive structure found in flowering plants The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs. • Increased by pollinators •Pollinators are attracted to flowers because of bright colors and they smell nice (same reason we like them) •Spreads pollen (sperm) to other flowers increasing genetic variation Plant Reproduction Mostly sexual reproduction • Some plants have a way of carrying out asexual reproduction Pollen is the male gametes of plants • Can be compared to sperm cells in animals Plants have ovules with eggs cells that can be fertilized by pollen The seed is an early embryo that can, in some cases remain dormant for long periods of time Covered seeds The seed coat protects the seed The endosperm (food supply) nourishes the embryo Seed protection Less likely to be eaten Protected from environment Nourishment for seed - better chance for survival Seed dispersal • Seeds have different shapes or protective coverings to aid in their dispersal • Adaptation: move away from parent plant or other seedlings – less competition Leaves Wide broad leaves provide additional surface area to absorb sunlight • Increase photosynthesis • However increase rate of water loss which could be bad- so how do plants over come this Adaptation to avoid water loss Cuticle: waxy covering on leaves (lipids – hydrophobic) – keep water from entering or leaving Stomata: openings in the bottom of the leaf that allow water to exit • Has guard cells on both sides of stomata to open and close Specialized leaves for habitat Water lilies: thick cuticle to keep water out Cacti Needles: same as pine needlesreduce surface area (water loss) – also provide protection Broad leaves- for areas of limited sunlight (rainforest floor) Can Plants Move? Plants cannot get up and walk like us, but they can move stems and leaves toward certain stimuli These movements are called tropisms Gravitropism Plant grows upward against the pull of gravity • Allows seed to grow up out of soil • Adaptation: to get sunlight Phototropism Plant grows toward light source To get sunlight for photosynthesis Thigmotropism A plant’s response to touch • Can be used as protection • Can be used for stability • Venus fly trap uses to obtain food(nutrients) Plant Hormones Important for growth and maturation • Are chemical substances that control a plant’s patterns of growth and development • Example: Auxin’s role in phototropism Auxin stimulates the elongation of cells When light hits the tip of a plant, more auxin is produced in the shaded area The dark side of the stem elongates causing the stem to bend toward the light Uses of plants Plants are a major food source for heterotrophs • Where do plants get their energy? They are autotrophic and photosynthetic Photosynthesis produces Oxygen Other uses Oils Medicine Lumber Aesthetics Shelter for animals Commercial products