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Chapter 14

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Biology 1225
Michael Butler

Chapter 14, Plants and Fungi ****Fungi are more evolutionarily related to animals than plants 14.2 Plant Traits and Evolution pg 265 bryophyte – member of an early evolving plant lineage that does not have vascular tissue; for example a moss cuticle – secreted covering at a body surface gametophyte – haploid gamete-forming body that forms in a plant life cycle lignin – compound that stiffens walls of some cells (including xylem) in vascular plants phloem – vascular tissue that distributes dissolved sugars plant – multi celled photosynthetic organism; develops from an embryo that forms on the parent and is nourished by it pollen grain – male gametophyte of a seed plant seed – embryo sporophyte of a seed-bearing plant packaged with nutritive tissue d a protective coat sporophyte – diploid spore-forming body that forms in a plant life cycle stomata – adjustable pores in a plant cuticle vascular plant – a plant that has xylem and phloem xylem – vascular tissue that distributes water and dissolved mineral ions 1 1. Plants evolved from freshwater green algae 2. Their life cycle includes two multi celled forms: a haploid gametophyte and a diploid sporophyte 3. The gametophyte dominates the life cycle of bryophytes, but the sporophyte dominates in vascular plants 4. Key adaptations to dry habitats include a waterproof cuticle and stomata, and internal pipelines of xylem and phloem 5. Lignin-reinforced xylem help vascular plants stand upright. 6. Seeds and male gametophytes that can be dispersed without water (pollen grains) evolved in seed plants Take Home Message What adaptive traits allow plants to live on land and in dry places? 1. Plants are multi celled, typically photosynthetic organisms that protect and nourish their multi celled embryos. They evolved from a lineage of green algae 2. Adaptations to life on land include a waxy cuticle with stomata, true roots, and vascular tissue that distribute materials and provide structural support 3. The plant life cycle alternates between two multi celled generations; a haploid gametophyte generation and a diploid sporophyte generation 4. The most recently evolved plant lineages produce pollen grains and seeds. These adaptations allowed the seed plant to spread into diverse habitats. 2 ***KNOW for EXAM**** Alternation of generations – is a term that refers to the fact that there are two distinct life forms of all plants, and these distinct forms generate each other. 1. The gametophyte form is haploid, and it makes gametes (egg and sperm) via mitosis 2. The sporophyte form is diploid and it produces spores via meiosis. 3. In some of the more evolutionarily primitive plants such as ferns, there are actually physically separate gametophytes and sporophytes, the fern gametophyte is a tiny little green plant that produces sperm and eggs, and when these unite (eggs from one gametophyte unite with sperm from another gametophyte) a fertilized cell called a zygote forms that then grows to form the large leafy fern sporophyte that you are familiar with. 4. In advanced plants, like the flowering plants, the sporophyte is dominant, it is much larger than the gametophyte – which is much reduced in size and consists of the reproductive parts in the flowers. ***Do not need to memorize the specific life cycle diagrams that are given for mosses and ferns etc. - with the exception of more primitive plants like mosses and ferns, plants spend the vast majority of their lives in the sporophyte stage. - So when you are looking at a tree you are looking at a sporophyte, the gametophyte structures are very tiny. - In non vascular plants like mosses and ferns the primitive characteristic of flagellated (swimming) sperm is retained, this is indicative of a reliance on the presence of free water in the reproductive process, something not seen in vascular plants, nearly all of which have non flagellated and thus non swimming sperm which are spread by means other than transport in water. 3 14.3 Nonvascular Plants (mosses) pg. 267(Bryophytes) mosses – most diverse group of bryophytes (non vascular plants) Low – growing plants with flagellated sperm disperse by producing spores. 1. Bryophytes include three lineages of low growing plants: a) mosses, b) liverworts, and hornworts. 2. Their flagellated sperm reach eggs by swimming through films of droplets of water that cling to the plant 3. The sporophyte begins development inside gametophyte tissues 4. The sporophyte remains attached to and often dependent upon the gametophyte even when mature Take Home Message What are bryophytes? 1. Bryophytes include three lineages of low growing plants (mosses hornworts, and liverworts) All have flagellated sperm and disperse by releasing spores 2. Bryophytes are the only modern plants in which the gametophyte dominates the life cycle and the sporophyte is dependent upon it 3. Liverworts are probably the oldest plant lineage. Hornworts are most likely the closest living relatives of vascular plants 4 14.4 Seedless Vascular Plants pg. 268 (Ferns) epiphyte – plant that grows on the trunk or branches of another plant but does not harm it ferns – most diverse lineage of seedless vascular plants rhizome – stem that grows horizontally along or just below the ground sorus – cluster of spore-forming chambers on a fern frond 1. Ferns are seedless vascular plants 2. Sporophytes dominate their life cycle and produce spores in sori. 3. Gametophytes produce flagellated sperm 4. Ferns grow from rhizomes (horizontal stems) 5. Some live on trees as epiphytes 6. Other seedless vascular plants include club mosses and horsetails 7. Coal formed from the remains of ancient non vascular seed plants Take Home Message What are seedless vascular plants? 1. Seedless vascular plants include ferns, club mosses and horsetails. 2. These plants disperse by releasing spores, and the life cycle is dominated by a sporophyte that has vascular tissue and lignin. The gametophyte is small and relatively short-lived 3. Like bryophytes, seedless vascular plants have flagellated sperm that must swim through a film of water to reach eggs. 5 14.5 Rise of the Seed plants pg. 271 megaspore – in seed plants, a haploid cell that gives rise to a female gametophyte (ovule) microspore – in seed plants, a haploid call that gives rise to a male gametophyte (pollen grain) ovule – of seed plants, chamber inside which megaspores form and develop into female gametophytes; after fertilization this chamber becomes seed. Pollen sac – of seed plants, chamber in which microspores from and develop into male gametophytes (pollen grains) Pollination – delivery of pollen to female part of a plant Secondary growth – increase
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