What is a Plant? with Plant Diversity Chapter 21 & 22
Multicellular eukaryote Produce their own food through photosynthesis Have thick cell walls made of cellulose Stems & leaves of most have a waxy waterproof coating called a cuticle What is a plant?
Scientists hypothesize that all plants probably evolved from filamentous green algae that lived in the ancient oceans Some of the evidence for their relationship can be found in modern members of both groups Origins of Plants
Green algae and plants have cell walls that contain cellulose 2. Both groups have the same types of chlorophyll used in photosynthesis and store food in the form of starch. Comparing Plants to Algae
The first evidence of plants in the fossil record began to appear over 440 million years ago These early plants were simple in structure and did not have leaves. They were probably instrumental in turning bare rock into rich soil The 1st plants
Preventing water loss: Most fruits, leaves, and stems are covered with a protective, waxy layer called the cuticle The waxy cuticle creates a barrier that helps prevent the water in the plant’s tissues from evaporating into the atmosphere Adaptations of Plants
2. Carrying out photosynthesis: The leaf, is a plant organ that grows from a stem and usually is where photosynthesis occurs Each plant species has unique leaves or leaflike structures Adaptations of Plants
3. Putting down roots: Plants can take in water and nutrients from the soil with their roots In most plants, a root is a plant organ that absorbs water and minerals usually from the soil Adaptations of Plants • Roots anchor a plant usually in the ground & function as storage.
Transporting materials: Water moves from the roots of a tree to its leaves, and the sugars produced in the leaves move to the roots through the stem A stem is a plant organ that provides support for growth. Adaptations of Plants
Transporting Materials • It contains tissues for transporting food, water, and other materials from one part of the plant to another • Stems also can serve as organs for food storage • In green stems, some cells contain chlorophyll and can carry out photosynthesis.
Transporting materials Phloem Xylem Xylem transports water and dissolved substances other than sugar throughout the plant. Phloem transports dissolved sugar throughout the plant. Cambium Cambium produces xylem and phloem as the plant grows.
Nonvascular Plants • Nonvascular plants do not have the conducting tissues xylem and phloem Examples: mosses, liverworts & hornworts
Nonvascular Plants Moss No true roots, stems, or leaves, must live near water or moist environment
Vascular Plants • Vascular plants have tubes and vessels to transport water and nutrients (Xylem & Phloem) Grass, trees, flowers, ferns • Vascular plants can live farther away from water than nonvascular plants.
Vascular Plant are divided into: • Seed Plants-flowers, pines, trees, grasses subdivided into: angiosperms-flowering plants gymnosperms-cone bearing plants • Seedless plants-ferns
Reproductive Strategies (1) • A seed is a plant organ that contains an embryo, along with a food supply, and is covered by a protective coat. • It also protects the embryo from drying outand also can aid in its dispersal Embryo Seed Coat Food Supply
In non-seeded plants (mosses & ferns) the sperm requires a film of water on the gametophytes plant to reach the egg Reproductive Strategies (2)
Reproductive Strategies (3) • In seed plants, which include all conifers and flowering plants, sperm reach the egg without using a film of water • This difference is one reason why non-seed plants require wetter habitats than most seed plants
In non-seed vascular plants such as ferns, spores have hard outer coverings Spores are released directly into the environment where they can grow into haploid gametophyte plants These plants produce male and female gametes Spores • Following fertilization, the sporophyte plant develops and grows on the gametophyte plant.
In seed plants, such as conifers and flowering plants, spores develop inside the sporophyte and become the gametophytes. The gameotophytes consist of only a few cells Male and female gametes are produced by these gametophytes Seeds • After fertilization, a new sporophyte develops within a seed. The seed eventually is released and the new sporophyte plant grows.
Non-seed plants include vascular or nonvascular organisms. Non-seed Plants • Non-seed plants are either vascular • Or non-vascular • There are 7 divisions of • Non-seeded plants. These • Plants produce hard-walled • Reproductive cells called • Spores
Small plants commonly called liverworts because the flattened body of the plant and it resembles the lobes of an animals liver They grow in moist environments They use osmosis & diffusion to transport water Found from Artic to Antarctic Some found in water, others in deserts Most have an oily/shiny surface Hepaticophyta: Liverworts
Thallose liverwort: have broad body that looks like a lobed leaf The body of a thallose liverwort is called a thallus. Found growing on damp soil 2 kinds of liverworts:
2. Leafy Liverwort: are creeping plants with 3 rows of thin leaves attached to a stem Leafy liverworts grow close to the ground and usually are common in tropical jungles and areas with persistent fog Their stems have flat, thin leaves arranged in three rows—a row along each side of the stem and a row of smaller leaves on the stem’s lower surface 2 kinds of liverworts:
Small Plants Sporophytes resembles the horns of an animal Nonvascular plant-grows in damp, shady habitats Relies on osmosis & diffusion to transport nutrients Anthocerophyta: Hornwort
Are the smallest division of nonvascular plants Currently consisting of only about 100 species are similar to liverworts in several respects Hornworts
Nonvascular plants Rely on osmosis and diffusion to transport materials Habitats include close to streams, rivers or humid tropical forest Limited in size (less than 5 cm tall) Cannot compete with vascular plants Bryophyta: Mosses
Mosses: More familiar than liverworts Small plant w/ leafy stems Grow in dense carpets or turfs Mosses have rhizoids, which help anchor the stem to the soil. Some have upright stems; others have creeping stems that lie along the ground or hang from steep banks or tree branches Mosses
Mosses • Some mosses form extensive mats that help retard erosion on exposed rocky slopes • Moses grow in a wide variety of habitats, even in the arctic during the brief growing season where sufficient moisture is present • A well-known moss is Sphagnum, also known as peat moss. • This plant thrives in acidic bogs in northern regions of the world. It is harvested for use as fuel and is a commonly used soil additive
Consist of thin, green stems. Are unique vascular plants because they have neither roots nor leaves Small scales that are flat, rigid, overlapping structures cover each stem. Psilophyta: Wisk Ferns • The two known genera of psilophytes are tropical or subtropical, only 1 found in U.S.
Vascular plants adapted primarily to moist environments Have stems, roots, and leaves Their leaves, although very small, contain vascular tissue Ancestors grew as tall as 30 m and formed a large part of the vegetation of Paleozoic forests Lycophyta: Club Mosses • The plants of these ancient forests have become part of the coal that is now used by people for fuel.
The club moss, Lycopodium, is commonly called ground pine because it is evergreen and resembles a miniature pine tree Some species of ground pine have been collected for decorative uses in such numbers that the plants have become endangered Club Moss
Vascular plants They have hollow, jointed stems surrounded by whorls of scalelike leaves The cells covering the stems contain large deposits of silica About 15 species of arthrophytes exist today Arthrophyta: Horsetails
Horsetail • Early horsetails were tree-sized members of the forest community. Today’s arthrophytes are much smaller than their ancestors • There are only about 15 species in existence, all of the genus Equisetum • These plants also are called scouring rushes because they contain silica, an abrasive substance • Most horsetails are found in marshes, in shallow ponds, on stream banks, and other areas with damp soil
The most well-known and diverse group of non-seed vascular plants. They have leaves called fronds that vary in length from 1 cm to 500 cm The large size of fronds is one difference between pterophytes and other groups of seedless vascular plants Pterophyta: Ferns Although ferns are found nearly everywhere, most grow in the tropics
Ferns • According to fossil records, ferns—divisionPterophyta—first appeared nearly 375 million years ago • Ancient ferns grew tall and treelike and formed vast forests
Fern Structures • In most ferns, the main stem is underground. This thick, underground stem is called a rhizome. Fronds Rhizome Root
Fern Structures • The leaves of a fern are called fronds and grow upward from the rhizome. • The fronds are often divided into leaflets called pinnae, which are attached to a central rachis. • The branched veins in ferns transport water and food to and from all the cells. • Fern spores are produced in structures called sporangia
Clusters of sporangia form a structure called a sorus (plural, sori). Sori are usually found on the underside of fronds but in some ferns, spores are borne on modified fronds Sorus
Were abundant during the Mesozoic Era. Today, there are about 100 species of cycads They are palmlike trees with scaly trunks and can be short or more than 20 m in height Cycads produce male and female cones on separate trees Cycadophyta: Cycads
Cones are woody strobili scaly structures that support male or female reproductive structures Seeds are produced in female cones. Male cones produce clouds of pollen Cones
Trees that bear cones are called gymnosperms Characteristics: produce seeds in cones (pines, firs, cedars) needle-like leaves Diversity of Cone Bearing Trees Male cones: produce pollen Female cones: contain seeds
Adaptations in Coniferophyta • The reproductive structures of most conifers are produced in cones. Wing Wing Pollen grain Two seeds Spores Ovule Pollen sac Male cones Female cone
Evergreen confiers: trees that are green year round & photosynthesize when conditions are right • Deciduous trees: lose their leaves each fall to conserve water through winter conditions