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Plants and Fungi By the end of this class you should understand: • The differences between algae, plants and fungi, and between groups of plants • The role of vascular structures in organisms • The reproductive cycles of different plants and fungi • The functions of major structures and materials unique to each group Algae, Plants, and Fungi • Algae, plants, and fungi are all different groups of living things – Easy to lump together because they are all immobile • Commonality: Cell walls! • Major differences exist between the three groups Structure and Lifestyle • Algae: Photosynthetic and have cell walls but their cells are not organized into tissues and organs – Also can’t live on land • Fungi: Have cell walls but are not photosynthetic – Fungi must grow on their food • Plants are photosynthetic and have tissues/organs Apparent Tangent: • If you want to build a building with bathrooms on every floor but you don’t have good pipes, how tall can you make the building? • If you have good pipes, how tall can you make the building? Plant Structures • A major development that separates most plants from algae is being vascular – A vascular plant has xylem and phloem • Vascular structures help bring water from roots up to the leaves, and sugar from leaves to the roots – Xylem brings water up – Phloem brings sugar down Algae, Mosses and Ferns • There are clearly more advanced structures in each of these groups – Algae are completely nonvascular and live in water – Bryophytes (including mosses) are plants that can live on land but are restricted in height because they are not vascular – Ferns are vascular plants • Date back to before the dinosaurs Moss & Fern Life Cycle • Mosses and ferns are clearly related because they have similar life cycles • Rather than produce gametes that immediately fertilize to make new plants, their gametes undergo mitosis and grow into a gametophyte • Gametophytes produce gametes through mitosis that fertilize to make a sporophyte Behold the Multistage Life Cycle! Additional Note on Plant Sex • Some plants are divided into male plants and female plants – One plant produces male gametes or pollen, another plant produces female gametes • Other plants are hermaphrodites, and each plant can make both male and female gametes – Some of these hermaphrodites can self-pollinate, others are restricted from doing so Plant-Only Structures • Plants grow their sturdy structures (including xylem and phloem) using carbohydrates – Made from photosynthesis! • Sugars linked into a mesh called lignin are super-durable – Wood is made with lignin • Cell walls are usually made of another carbohydrate compound called cellulose Additional Plant Structures • Unlike algae, plants can grow on land – Use lignin to stand up straight – Use vascular structures to bring water into plant • Plants have different organs to adapt to living on land – Roots – Stems – Leaves Plant Groups • Bryophytes – Mosses • Seedless vascular plants – Ferns • Seed plants – Gymnosperms • Plants with pinecones (pine, redwood, etc) – Angiosperms • Flowering and fruiting plants Bryophytes • Mosses and similar small plants such as liverworts • The large part of the plant is usually the gametophyte (haploid) – Produces small sporophytes that produce new spores through meiosis • No xylem/phloem, allow nutrients and water to diffuse across its surface – Thus limited in size Seedless Vascular Plants • Ferns are the most common example of seedless vascular plants – Seedless: sporophyte/gametophyte stages – Vascular: have xylem/phloem so can get tall • The sporophyte is the main plant – Gametophytes are produced by the small structures on the underside of the leaves – Produce spores that grow into new ferns Seed Plants • Seeds are a more recent invention of plants – First gymnosperms appeared around 300 million years ago • Seeds are useful because they are durable and can wait for the right moment to start growing – As opposed to new sporophytes which don’t have a protective covering at any point • Divided into gymnosperms and angiosperms Seed Structure • Seeds are formed from the fertilization of a microspore (pollen) and megaspore (ovule) – This occurs at the flower • A seed always has a protective coating around the new embryo, stored food for the embryo, and usually a delivery system for getting it away from the parent plant – In angiosperms this delivery system is called a fruit (not always delicious) Gymnosperm • Gymnos refers to nudity – The gymnasium is so called because the Greeks always exercised naked • Gymnosperms have “naked seeds” with no fruit – Does have a protective armor around the seeds – These are what we think of as pinecones • Pines, redwoods, conifers Angiosperm • Angiosperms have flowers for improved fertilization – All other plants must depend on wind fertilization only, and some angiosperms do as well • Angiosperms all produce fruits for their seeds – The fruit serves as a delivery system for separating the offspring from parents (seed dispersal) – Reduces competition Examples of Seeds and Fruits Flower Anatomy • Flowers vary wildly in structure (of course) but all have certain features in common: – Petals (often to attract pollinators) – Stamen (produce pollen) – Carpel (holds ovule and allows fertilization) • Flowers often have some method of attracting animals to bring the pollen from one flower to another – Edible pollen – Nectar – Structures that resemble female insects Generic Flower Fungi • Fungi diverged from protists around the time of the Cambrian Explosion (500+ mya) • Fungi are actually more closely related to animals than to plants – Their cell walls are made of chitin, the same material in an insect exoskeleton • Mushrooms, molds, and yeasts are all fungi Fungal Anatomy • All fungi live as tiny interconnected threads that grow inside their environment such as the soil – Each thread is called a hypha (plural hyphae) – A cluster of hyphae is called a mycelium • The large cap that grows out of the ground is the reproductive fruiting body of the fungus which remains buried underneath Fungus Food • Fungi grow on their food and digest it externally – No internal digestive system • By secreting enzymes on their food, they break it down, then absorb the nutrients through their cell walls – Nutrients can diffuse from one cell to the next, but they have no vascular system and so are limited in height Giant Fungi? • Since fungi have no vascular system they cannot grow very tall – They can, however, grow sideways a very large distance • The largest known organism on earth is a fungus that covers at least 4 square miles (over 2000 acres) in Oregon – WTF Hyphae in Action • Many fungi do not produce any fruiting body and are entirely made of hyphae – These are called molds or yeasts • The hyphae are actually haploid and only fertilize to make a zygote during mating season – The zygote immediately undergoes meiosis to make more hyphae Mushroom Anatomy • In mushroom species, the stalk and cap are formed by the hyphae after they have undergone cytoplasmic fusion – This means that two haploid cells have fused their cytoplasm but not their nuclei – This is written as the cells being n+n instead of 2n • In the mushroom cap, the nuclei fuse, a zygote is formed, and then it undergoes meiosis to make more new spores for hyphae Fungus Environments • Fungi grow on their food since they can’t chase after it – Fungal spores are spread by the wind and land on all sorts of things that are edible • Many fungi grow in soil eating dead things • Some fungi grow on our food (bread molds) • Some fungi grow on our flesh! Fungal Infections • Fungi that grow on a living thing are using a parasitic feeding strategy • In humans and other animals, fungal infections can be a source of disease (athlete’s foot, yeast infections, ringworm) • Many fungi can grow on specific plants and kill them for food (often called rusts) – The famous potato blight in Ireland was a protist similar in structure to a fungus Fungi as Partners • Some fungi live in a symbiotic relationship (mutually beneficial) with other organisms • Lichen are a composite organism with algae or cyanobacteria living inside the cell walls of fungi – How does each side benefit? • Some fungi grow on roots of plants, call mycorrhizae (singular: mycorrhiza) – How does each side benefit? See you in lab!