Botany Midterm Review PDF

Botany week 5: Midterm review Roots ▪External structures ▪ Internal structures ▪ Root types and modifications Functions of roots ▪ Anchorage ▪ Absorption ▪ Conduction ▪ Food storage Characteristics of roots -Cylindrical in form -Lack nodes and...

Botany week 5: Midterm review Roots ▪External structures ▪ Internal structures ▪ Root types and modifications Functions of roots ▪ Anchorage ▪ Absorption ▪ Conduction ▪ Food storage Characteristics of roots -Cylindrical in form -Lack nodes and internodes -Lack buds, leaves and flowers -Generally branching (generally, if: Below ground: root system Above ground: shoot system) Radicle ▪ Primary root ▪ First root to emerge from a seed Root types/root system ▪ Diffuse or fibrous ▪ Taproot or primary system ▪ Adventitious roots ▪ Diffuse or fibrous roots - generally thin - hair-like and numerous smaller root branches - better able to hold soil - gives better stability - cannot tolerate drought - occurs in monocot ▪Taproot or primary root - presence of a primary or main root - with minimal branching - consisting of secondary, smaller lateral roots - occurs in dicot plants ▪ Adventitious roots - roots that arise above ground - arise from leaf or stem - same functions as roots - e.g. Corn  Specialised roots: Prop/stilt roots - adventitious roots - roots that arise above ground - arise from leaf or stem - same functions as roots - common in monocots - e.g. Corn Fleshy roots - a taproot system - heavy and thick root - has the main root enlarged in size - does not have many branches - often used for human or animal consumption Fascicled roots - fibrous root system - presence of swollen bulb-like parts in the roots - used to store food Aerial roots - grow above ground parts of a plant - as anchor - also absorb moisture and nutrients Buttress roots - are large, wide roots on all sides of a shallowly rooted tree - swollen bases or braces - hold the trees upright - aid in the extensive distribution of the shallow roots - common in tropical rainforest trees Pneumatophore - aerial breathing roots - grow out from the water surface - facilitate aeration necessary for root respiration - common in mangroves Contractile roots - adventitious roots - develop from the base of the stem of a bulb or corm - contract and pull the plant to a desirable depth in the soil - found on bulbs or corms  Photosynthetic roots - assimilatory roots - green roots and perform Photosynthetic activity - absorb moisture from the Atmosphere Parasitic roots - adventitious roots of parasitic plant - penetrating into the conducting tissues of the host plant Roots- producing suckers Root suckers, or root sprouts, are a tree's natural response to wounding or stress. Mycorrhizal roots - with symbiotic association with a soil fungus that helps the plant absorb essential minerals from the soil External structures of root Root cap - thimble-shaped mass of parenchyma cells at root tips - protects the root apical meristem, where cells divide - secretes mucilage to ease the movement of the root through soil Quiescent center - behind the root cap - region of inactive cells - function as a cellular reserve - also important in organizing the patterns of primary growth in the root Region of cell division - meristematic region - new cells are formed via mitosis - small cells, nearly cube-like - with thin cell walls - very distinct nucleus Region of cell elongation Embryonic tissues/generative tissues - Protoderm - Ground meristem - Procambium - area of cell enlargement - cells increase in length up to 10x their original length - cells are mature and columnar in shape Region of cell differentiation - above the elongation region - youngest part of this region is root hair zone - root hairs evident -the embryonic tissues undergo modifications: o protoderm to epidermis o ground meristem to cortical cells (cortex and pericycle) o procambium to vascular tissues (xylem and phloem) and pith Internal structures of root Epidermis -one-cell thick that covers the root except the root cap -lacks stomata -lacks cuticle and with root hairs -absorbs water and dissolved material from the soil Cortex - formed by the ground meristem - occupies the largest cross-section of the root - with 3 layers o hypodermis - outermost layer with suberin - protects the root - food and water storage o parenchyma cells - make-up most of the cortex - often contain starch and separated by large intercellular spaces - stores reserves for subsequent use  o endodermis - innermost layer controls the amount of and kinds of water and dissolved materials that enter the xylem in root’s center - cells are packed tightly - each cell has a special bandlike region (Casparian strip) (Dicot root) Pathways of water into roots - plasmodesmata Casparian strip (waterproof) - lined with lignin and suberin - prevents water and dissolved minerals from passing into the stele along endodermal cell walls - water and dissolved minerals pass through PM of endodermal cells Stele - cylindrical of vascular tissues - with 3 layers Pericycle – outermost layer which is one to several layers of parenchyma cells – remains meristematic – gives rise to branch roots (secondary or lateral roots) Xylem – centermost tissue of stele – often has two, three, four, or more extensions (xylem arms) Phloem – located in patches between xylem arms Vascular cambium – gives rise to secondary tissues in woody plants – sandwiched between xylem and phloem Pith – centermost tissue of stele – consists of parenchyma cells Phloem and Xylem – in separate alternating strands that in cross section are arranged in a circle around the centrally pith Monocots – do not have secondary growth – no vascular cambium exists in roots – cortex expands Initiation of secondary growth - pericyle cells opposite the xylem points start to make periclinal divisions - inner layer of cells becomes the vascular cambium - outer layer is retained as pericycle - vascular cambium is continuous around the primary xylem Continuation of secondary growth - the vascular cambium continues to divide periclinally - the daughter cells differentiate into secondary xylem cells or secondary phloem cells - the pericycle resumes its meristematic character and begins to divide periclinally (phellogen or the cork cambium) - the cork cambium forms phellum cells (cork cells) towards the outside of the plant - the cork cambium also produces the Phelloderm STEMS A stem is a collection of integrated tissues arranged as nodes and Internodes. Nodes – where leaves, buds, flowers attach Internodes – between nodes Functions of the stems ▪ Support leaves and reproductive structures ▪ Provide internal transport ▪ Produce new living tissues ▪ Some are modified to store food ▪ If green, to manufacture carbohydrates by photosynthesis ▪ Support leaves and reproductive structures ▪ Produce new living tissues ▪ Provide internal transport ▪ Some are modified to store food ▪ If green, to manufacture carbohydrates by photosynthesis Radicle -The first stem that develops from a seed arises from the epicotyl, an embryonic shoot within the seed. Herbaceous stem - Lacks secondary growth - Grow to a small diameter - Stems remain soft and flexible - Buds lack protective scales - Covered with epidermis - Lives only for one season - monocot Woody stem - Has secondary growth - Increasing diameter of the stem - Covered with periderm or bark - Lives year after year - Dicot types of stems (visibility of stem) Acaulescent - with no obvious stem above the ground - only the leaves are seen - e.g. Grasses Caulescent - with obvious stems above the ground, as in most stems Types of stems (texture) ▪ Herbaceous - appear soft and fleshy - often live only for a short period of time ▪ Woody - forms permanent woody tissues - hard and usually covered with bark ▪ Suffrutescent - more or less woody - or only a part of the base is woody - e.g. at the base types of stems (direction of growth) -Erect - ascends perpendicularly to the ground -Ascending - stem rises obliquely -Decumbent -more or less reclining on the ground -Prostate/procumbent - lying flat on the ground -Creeping - when closely pressed to the ground and rooting at the nodes with runners or stolons -Scandent/climbing -stems ascend by means of support Types of stems (location) ▪ Stems that grow aboveground Tendrils - long coiling structures - function for attachment and support of climbing plant stolons/runners - horizontally oriented stem - grow along the soil surface - function for vegetative reproduction - e.g. Strawberry, bermuda grass Thorns - modified stems - protect the plant from grazers - e.g. Bougainvillea cladodes/cladophylls - flat stems - leaf-like stems - modified for photosynthesis - e.g. Asparagus, cactus culms - hollow or solid stem - with distinct nodes and internodes - sometimes form roots at the nodes - e.g. Sugarcane and bamboo succulent stems - store large amounts of water - common with plants in desert areas - e.g. Cactus ▪Stems that grow underground Bulb - large, roundish bud - with small basal stem at its lower part - its bulk being made of thickened scales which store nutrients - e.g. Onions, tulips Corm - stubby, short, fleshy, vertically oriented stems that store nutrients - e.g. Gabi, gladiolus Rhizomes - grow horizontally near the soil surface - short internode bearing scales - roots and buds develop at the nodes and grow into new plants - store food - e.g. Ginger Tubers - swollen regions of stems that store food - bear buds called eyes - e.g. Potatoes External structures of stems Bud - undeveloped shoot - contains embryonic meristems - maybe terminal or axillary Terminal bud - found at the tip of the stem Axillary buds ○ also called lateral buds ○ found in the axils Terminal and axillary buds - form stems with leaves or flowers when they grow Bud scale - modified leaves - an outer protective layer - covering a dormant terminal bud - protects the lateral bud and terminal bud Bud scale scars - develop when the bud scale fall off Leaf scar - shows where the leaf was attached to the stem Bundle scars - tiny bumps, small dots, or raised bumps in leaf scar - broken ends of the vascular bundles passing from the stem into the Leaves Lenticels - sites of loosely arranged cells that allow gas exchange - look like tiny marks or specks - often used as an aid in identifying the plant Node - the area on a stem where one or more leaves is attached Internode - the area on a stem between two successive nodes Epidermis - outer covering - provides protection - with cuticle Cortex - a cylindrical several cell thick - part of the plant’s ground tissue system - complex tissue (parenchyma, collenchyma, sclerenchyma cells) Vascular tissues - provide support and conduction - extend as long strands throughout the length of the stem - continuous with the vascular tissues of both roots and leaves Dicot cross section Vascular bundles - a cylindrical several cell thick - part of the plant’s ground tissue system - Xylem (inner side) - Phloem (toward the outside) - Vascular cambium (sandwiched between xylem and phloem) Vascular bundles - Xylem (inner side) o tracheids o vessel elements - Phloem (toward the outside) o fibers o phloem fiber cap Pith - center of the herbaceous dicot ground tissue - large, thin-walled parenchyma cells (for storage) Monocot cross section Vascular bundles -scattered throughout the stem -each bundle enclosed in a bundle sheath of sclerenchyma cells for support Ground tissue - where the vascular tissues are Embedded - performs the same functions as cortex and pith in dicot stems Monocot stem (herbaceous) - no lateral meristems - with primary growth only - do not produce secondary tissues wood and bark Stems of woody plants Secondary growth - activity of two lateral meristems ▪ Vascular cambium – gives rise to secondary vascular tissues - secondary xylem (wood) - secondary phloem (inner bark) ▪ Cork cambium (phellogen) – cells of the outer lateral meristems - cork cells - cork parenchyma (phelloderm) Periderm (outer bark): cork cambium + cork cells + phelloderm Secondary growth (dicot stem) The vascular cambium differentiates between the primary xylem and primary phloem and forms an open-ended cylinder. The vascular cambium produces secondary phloem to the outside and secondary xylem (wood) to the inside. Secondary xylem - conducts water and dissolved minerals from roots to leaves - contains the same types of cells (tracheids, vessel elements, parenchyma cells, fibers) Secondary phloem - conducts dissolved carbohydrates (sucrose) form the leaves to stem or roots contains the same types of cells (sieve-tube elements, companion cells, parenchyma cells, fibers) Rays - chains of parenchyma cells - radiate out from the center of woody stem - formed by vascular cambium - continuous with the secondary xylem and secondary phloem - pathways for lateral transport of water and dissolved materials from secondary xylem to secondary phloem; - transport of dissolved carbohydrates from secondary phloem to secondary xylem Cork cambium (phellogen) produces periderm ▪ a continuous cylinder of dividing cells (similar to vascular cambium) ▪ or a series of overlapping arcs of meristematic cells that form from parenchyma cells in cortex and secondary phloem Cork cells (phellem) formed to the outside of the cork cambium. - dead at maturity, heavily suberized, or waterproofed, walls - protect the woody stem Cork cells are impermeable to water and gases, yet the internal tissues of woody plant must exchange gases with the surrounding atmosphere. Cork parenchyma formed to the inside of the cork cambium. - one to several cells thick, much thinner than cork cell layer -stores water and food (as starch granules) Thickening of stem due to secondary growth - epidermis and stomata die - stomata replaced by lenticels Bark - old, inactive secondary phloem Sapwood - secondary xylem - younger, light colored wood, closest to the bark - wood of conifers Heartwood - older wood in the center of the trunk - typically a brownish red wood of flowering plants not conducting water Leaves Functions of Leaves ▪ Manufacture of food ▪ Gas exchange ▪ Protect the vegetative and floral buds ▪ Water transport ▪ Store food during germination ▪ Horticultural uses - Food - Ornamental - Herb - Summer cooling - Medicinal values - Beverage - Wildlife habitat - Aromatic oils and wax - Propagation from cuttings External structures of a dicot leaf Leaf blade – wide flattened area where photosynthesis takes place Apex – pointed end Margin – edge of the leaf Veins – vascular bundles within leaf for transpiration  Midrib – primary vein which consists of vascular bundles-food nutrients and water conduction; helps to keep the leaf in an upright position and to keep the leaf strong with protection from the wind; also supports the leaf to be exposed to the sunlight. Base - leaf base is the slightly expanded area where the leaf attaches to the stem. Petiole – short stem that attaches leaf to main stem or branch Axillary bud – baby leaf or stem Stipule – leaf like outgrowths usually present in pairs at the base of the petiole External structures of a monocot leaf In the absence of petioles in grasses and many other monocots, the base of the leaf forms a sheath that envelops the stem. Sheath – part of leaf that holds leaf to stem. Auricle - two additional flaps of leaf tissue, extend around the stem at the juncture of the sheath and blade. Ligule - a small flap of tissue, extending upward from the sheath Collar – area between the leaf sheath and blade; auricles and ligules are on the inside of this area. Internal structure of a leaf Three tissue systems - Dermal tissue system - Ground tissue system - Vascular tissue system Dermal tissue system: Epidermis - Upper epidermis Structures in epidermis: - Stoma or stomata -small pore flanked by guard cells in the epidermis -for gas exchange - Guard cells -a cell in the epidermis of a stem or leaf -two guard cells form a pore (stoma) Lower epidermis with clear, transparent cells to allow light to reach the photosynthetic tissues - mostly parenchyma cells (no chloroplasts) Function: - provides protection for the inner tissues - secretes cuticle (waxy substance or cutin) Cuticle - the outermost layer of both the upper and lower surfaces of the leaf - clear and waxy to prevent against water loss Mesophyll - photosynthetic tissue - from Greek word meaning “the middle of leaf” - with parenchyma cells packed with chloroplasts - with many air spaces Types: - Palisade mesophyll cells ○ main site of photosynthesis ○ vertically elongated, compactly arranged parenchyma cells - Spongy mesophyll cells ○ allow diffusion of gases ○ with more loosely and more irregularly arranged cells Vascular tissue system: Veins or vascular bundle ▪ Xylem ○ conducts water and dissolved minerals ○ on upper side of vein, toward the upper epidermis ▪ Phloem ○ conducts dissolved sugars ○ confined to the lower side of vein Bundle sheath - a ring of parenchyma or sclerenchyma cells - surrounds the vascular bundle in a leaf Leaf types ▪ Simple ○ Leaf blade is one continuous unit ○ Composed of a single leaf and a petiole ○ ▪ Compound ○ Several leaflets arise from the same petiole ○ Contain a rachis ○ Two types: pinnately compound ○ and palmately compound ▪ Compound - Pinnately compound o leaflets arranged on both sides of a common rachis - Palmately compound o leaflets radiate from one central point Leaf arrangement on stem ▪ Alternate – one leaf at each node ▪ Opposite – two leaves grow at each node ▪ Whorled – three or more leaves grow at each node ▪ Rosette – circular arrangement of leaves Leaf Venation ▪ Netted or reticulate venation ○ one or a few prominent midveins from which smaller minor veins branch into a meshed network Common to dicots and non-flowering plants - Pinnately veined - main vein called midrib with secondary veins branching from it (eg. mint, basil) - Palmately veined - veins radiate out of base of blade (eg. maple leaf) ▪ Parallel - veins are parallel to one another (eg. Corn, snake plant) ▪ Dichotomous - no midrib or large veins - individual veins have a tendency to fork evenly from the base of the blade to the opposite margin, creating a fan-shaped leaf (eg. Ginkgo) Most dicots have branch-like veins and palmate leaf shape Monocots have parallel leaf veins and longer, slender blades Leaf types - angiosperms (flowering plants) Leaf types - gymnosperms Leaf shapes - angiosperms  Leaf margins - angiosperms Modified leaves ▪ Bud scales -Protect delicate meristematic tissue of the bud from injury and drying out ▪ Tendrils - Aid in climbing ▪ Colorful bracts -Associated with a flower or inflorescence but not part of the flower ▪ Bulb -Rounded, fleshy underground bud that consists of a short stem with fleshy leaves ▪ Prickles and spines - Epidermal outgrowths - For protection ▪ Storage leaves/ succulent leaves - Retain water in large vacuoles ▪ Reproductive leaves - Plantlets arise on margins of leaves ▪ Insect-trapping leaves - For capturing insects ▪ Winged petiole - Additional surface for photosynthesis ▪ Enlarged petiole - Filled with air for buoyancy Sexual Reproduction of plants Biological function of flowers ▪ Sexual reproduction - fusion of egg cell and sperm cell - fertilization in the flower’s ovary - production of seeds inside the fruits ▪ Asexual reproduction - no fusion of gametes - from a vegetative structure Flower structure 4 kinds of organs ▪ Pistil- the female reproductive part of a flower. Ovary – contains the ovules and becomes the fruit. Ovule – becomes the seed when sperm cell fertilizes the egg cell. ▪ Petal- sticky pollen-receptive part of the pistil, colorful part of a flower used to attract insects and birds. Corolla – collective term for all the petals. ▪ Sepal- the stalk of the pistil down which the pollen tube grows.protects the bud of a young flower. Calyx – collective term for all the sepals. ▪ Stamen- hollow tube which develops from a pollen grain when deposited on a stigma. male reproductive part of a flower. Anther – produces pollen grains which develop sperm. Pollen – immature male gametophyte. Filament – supports the anther. Other flower parts Perianth – corolla + calyx Receptacle – reproductive parts of a plant are attached here. Peduncle – flower stalk. Classification of flowers ▪ According to class ▪ Based on radial symmetry ▪ According to class ▪ Based on the presence of reproductive organs ▪ Based on position of ovary ▪ Based on the pistils ▪ Based on the number of flowers Inflorescences ▪ Clusters of flowers ▪ All flowers arising from the main stem or peduncle ▪ Florets are the flowers included in the inflorescence Common inflorescences ▪ Spike - Individual flowers are sessile - Lower flowers open first - Indeterminate ▪ Raceme - Individual flowers have pedicel - Pedicels vary length from species to species - Lower flowers open first - Indeterminate ▪ Panicle - A highly branched inflorescence consisting of many, repeating units - Panicles can be made of many spikes, racemes, corymbs, or umbels - Indeterminate ▪ Umbel - Individual flower pedicels all originate from the same spot on the peduncle - Outer flowers open first - Often, umbels are globe-shaped - Indeterminate ▪ Corymb -Somewhat similar to the umbel -Individual flower pedicels are attached to the peduncle at different points -Often flat-topped -Outer flowers open first -Indeterminate ▪ Cyme -In real life, cymes tend to be flat or convex shaped -The inner flowers open first -Determinate ▪ Compound cyme  ▪ Composite head ○ A highly advanced inflorescence. ○ Consists of separate ray and disk flowers ○ Bracts may be green but can also be colored (ex: Helianthus annuus, Sunflower, produces a large composite head. ▪ After pollination and fertilization, each ▪ disk flower becomes a single-seeded fruit.) ▪ Echinacea purpurea, Purple Coneflower (image courtesy of Wildflower Farm). ▪ Composite head with purple ray flowers and brown disk flowers. Pollination ▪ The transfer of pollen grains from the male anther to the female stigma ▪ Two types - Self-pollination - Cross-pollination Methods of pollination ▪ Wind-pollinated plants ○ Produce many small, inconspicuous flowers ○ Large, colorful petals, scent, or nectar are not produced ○ Some have large, featherly stigmas, presumably to trap wind-borne pollen grains ○ Produce large quantities of pollen grains ▪ Animals ○ Insects – bees, wasps, flies, butterflies, moths ○ Birds ○ Mammals ○ Reptiles and amphibians  ▪ Insect Pollination ○ Pollinate about 70% of all flowering species ○ Insect pollinated flowers have blue or yellow petals ○ Nectar guides direct insects to the center of the flower where the pollen grains and nectar are ○ Insects have a well-developed sense of smell ○ Many insect-pollinated flowers have strong scents that may be pleasant or foul to humans 1. Insect pollinators: Bees ▪ The most important group of flower pollinators ▪ Bee-pollinated crops provide about 30% of human food ▪ Guided by sight and smell ▪ See yellow and blue colors not red ▪ Flowers have “honey guides” and bee landing platforms ▪ Bumblebees and honeybees) 2. Insect pollinators: Moths and butterflies ○ Also guided by sight and smell ○ Butterflies can see red and orange flowers ○ Usually shaped as a long tube because of insect’s proboscis – to get nectar ○ Moth-pollinated flowers are usually white or pale, with sweet, strong odor – for night pollination) 3. Insect pollinators: Flies and beetles ▪ Syrphid flies or flower flies pollinate flowers ▪ Not as hairy as bees and as efficient in carrying pollen, but some are good pollinators ▪ Beetles pollinate flowers that have very strong odor) Animal pollinators: Birds ▪ Have a good sense of color, they like orange, yellow or red flowers ▪ Do not have a good sense of smell, so bird-pollinated flowers usually have little odor) ▪ Mammals ○ Bat-pollinated flowers are night blooming ○ Bat-pollinated flowers are often have dull white petals and a strong scent Water -Pollen floats on water -Deposited inside the flower upon contact -Australian sea grass and pond weeds Pollination and fertilization ▪ Pollination: a method to get the pollen from the male anther to the stigma. ▪ Fertilization: union of an egg and sperm cells. Double fertilization 1. The pollen grain adheres to stigma, contains two cells (generative cell and a tube cell). 2. The pollen tube cell grows into the style. The generative cell travels inside the pollen tube. It divides to form two sperm cells. 3. The pollen tube penetrates an opening in the ovule (micropyle). 4. One of the sperm fertilizes the egg to form the diploid zygote. The other sperm fertilizes two polar nuclei to form the triploid endosperm, which will become a food source for the growing embryo. ▪Fruit types and seed dispersal Fruit ▪ A mature, ripened ovary ▪ Provides protection for the enclosed seeds ▪ Aids in seed dispersal ▪ May contain one or more seeds Classification of fruits According to development - Normal fruit- develops through fertilization - Parthenocarpic fruit- develops without fertilization (GMO) According to origin - Simple fruit - arises from a single ovary. They are classified into various kinds according to their consistency, structure, and dehiscence.  - Multiple fruit - results from the development of separate flowers in a compact inflorescence. - Aggregate fruit - arises from the development of separate ovaries in one flower. According to pericarp texture - Fleshy fruits -fleshy and soft pericarp. - Dry fruits dry and hard pericarp Types of fruits Simple fruit -develops from the carpels of closely associated flowers that fuse or grow together. 1. Berry - Fleshy fruit - Fruit wall is soft throughout Ex. Tomato, grapes, blueberries, cranberries, banana) 2. Pepo - Modified berry - Fruit wall is leathery rind Ex. Pumpkin, squash, cucumber, watermelon 3. Hesperidium - Modified berry - Fruit wall is leathery with numerous oil glands surrounding the succulent cavities where the seeds occur Ex. Citrus fruit 4. Drupe - Fleshy fruit - Inner wall of fruit is hard and stone Ex. Peach, cherries, avocado, olives, Almonds 5. Follicle - Dry fruit that splits open along one suture to release its seeds - Fruit is formed from ovary that consists of a single carpel Ex. Milkweed 6. Legume - Dry fruit that splits open along two sutures to release its seeds - Fruit is formed from ovary that consists of a single carpel Ex. Green pea 7. Capsule - Dry fruit that splits open along two or more sutures or pores to release its seeds  - Fruit is formed from ovary that consists of two or more carpels Ex. Iris, cotton 8. Caryopsis - Dry fruit - Fruit wall is fused to the seed Ex. Wheat, corn 9. Achene - Dry fruit - Fruit wall is separate from the seed coat Ex. Sunflower 10. Nut - Dry fruit that has a stony wall - Usually large - Does not split open at maturity Ex. Oak, chestnuts, hazelnuts ▪ Aggregate fruit -develops from a single flower with several to many pistils (i.e., carpels are not fused into a single pistil). Ex. Blackberry, raspberries ▪ Multiple fruit -Multiple fruit – develops from the ovaries of a group of flowers. Ex. Mulberry, pineapple, figs ▪ Accessory fruit -a fruit whose fleshy part is composed primarily of tissue other than the ovary. Ex. Apple, pears Seeds Seed dispersal ▪ Self dispersal - explosive fruits - popping mechanism for short distance dispersal - detaches and blows across the ground, scattering seeds as it bumps along ▪ Animal dispersal - carry seeds on fur or feathers - attach and cling to animals - eat edible fruits that contain seeds and pass through digestive system to be deposited later - collect and bury seeds (ants and squirrels) ▪ Wind dispersal - fruits and seeds may have special devices for wind dispersal - some plants have seeds within  fruits acting as kites or propellers that aid in wind dispersal - plant dries up and is blown across fields and roads, dispersing seeds as it tumbles ▪ Human dispersal - seeds stick into socks, shoes, and other clothing - vehicles and farm machinery can get seeds and plant parts caught underneath - removing the seeds from the cob first and then planting them ▪ Water - seeds of hard, dry fruits can float and travel on the water until washed up on shore - coconut has air spaces that make it buoyant and capable of being carried by ocean currents ▪ Nature - where nature fires are common, many seeds require intense heat to break dormancy - seedlings more abundant after fire has cleared away competing vegetation