Semester 1 Bio 2025 Lecture Notes PDF

Lecture 1 Agriculture - domestication of plants - domestication of animal - Iraq, wheat Invented: - 10 000 years ago in multiple locations Consequences - Permanent villages, towns, cities - Larger families = larger population - Diverse economy - Less coo...

Lecture 1 Agriculture - domestication of plants - domestication of animal - Iraq, wheat Invented: - 10 000 years ago in multiple locations Consequences - Permanent villages, towns, cities - Larger families = larger population - Diverse economy - Less cooperation - Socioeconomic classes - Separation of humans from rest of nature - Larger-scale war Examples: - Chocolate plant - Gasoline was derived through a plant 300 million years ago - Rubber o 1/3 of rubber comes from plants o Car tiers come from scoring the sap of the trees - Clothes o Cotton ▪ Cellulose, polymer (glucose) DRUGS: PLANTS SECONDARY COMPOUNDS - this means those compounds are not necessary for metabolism, growth and development o around 200,000 compounds Where do seeds come from? - Flower - Fruit - seeds Examples: - Quinine o Bark of cinchona tree o South America, now widely introduced worldwide o Treats malaria from 1650 in Europe o Treats ▪ Anemia ▪ Muscle spasms ▪ Cancer ▪ Tonic water (bitter water) - Caffeine o Coffee tree o Yemen, Ethiopia - Aspirin - willow species o Acetylsalicylic Acid o Treats Pain, Fever, inflammations, is a blood thinner, tooth aches - Tetrahydrocannabinol THC (Marijuana) - Nicotine (tobacco) - Opium poppy Papaver o Opium, o Heroin o Morphine o Codeine - Taxol from yew o Cancer treatment ▪ Chemotherapy for ovarian, breast and lung cancers Hoh rainforest - Plants make the oxygen and energy used by other components of terrestrial ecosystems o Plants make ½ of the oxygen, marine do the other ½ Plants Importance: - Energy o Food (agriculture) o Fossil fuels - Clothing - Drugs and medicines - Ecosystem functioning - Biodiversity Botany - The study of plants Evolution o Ecology o Community o Population Molecular genetics o Mathematical modeling o Leaf shape in different ecosystems/ Environment o Plants population growth Morphology o External Features Anatomy o Internal features Physiology o Cell biology o Cellular components Systematics o How to group organisms Development o Developmental and formation of plants Cardinal Flowers - Plants is first male then becomes female - Top are male bottom are females - Top flowers are the youngest and the bottom are the oldest Self-fertilization 1. Ruby throated hummingbird goes to the male flower a. Male flower is closer to the top 2. Takes the nectar a. Bird now has the pollen on its head 3. Bird goes to female flower near the bottom a. Pollen gets transferred into the female and self-fertilization occurs What is a plant? - Viridiplantae clade o Chlorophytes (Green algae) ▪ Originally marine o Charophytes o Embryophytes = Land plants - Plants (green and red algae) o Form primary endosymbiosis ▪ Prokaryote + eukaryote = Eukaryote ▪ No photosynthetic eukaryote engulfed a photosynthetic cyanobacterium (now a plastid = chloroplast) When do plants appear in the history of life? Earth forms o 4550 MY Photosynthesis appears (Cyanobacteria) o 3500 MY Oxygen revolution o 2400 MY Multicellular eukaryotes – 1st plastid; plants and read algae diverge o 1500 MY Colonization of land by plants, fungi then animals o 500 MY When do plants appear in history - Plants split from red algae o 1500 mya = 1.5bya o Both single-cell and multicellular forms o Marine o Moist environments near ocean shores - 500 mya: colonization of drier environments o Adaptations: ▪ Cuticle ▪ Vascular tissue Roots and shoots ▪ Relationship with fungi ▪ Seeds and pollen - Since colonizing land o 290 000 species Viridiplantae Features of all plants 1. Starch as main energy storage molecule a. Polysaccharides (carbohydrate) of glucose residues i. Amylose (20%) chain/ unbranched ii. Amylopectin (80%) Branched b. Why not Sugar, sugar is … i. Not very reactive ii. Easily metabolized iii. But absorbs and holds water iv. THEREFORE STARCH IS THE SOLUTION 2. Chlorophyll B a. Chl a i. All photosynthetic eukaryotes b. Chl b i. Accessory pigment, passes energy to chl a ii. Chl b absorbs slightly different wavelengths 3. Cellulose is major component of cell wall a. Polysaccharide i. Unbranched glucose residues ( different bonds from starch) b. Most common organic polymer on earth c. Cotton is 90% cellulose d. Used to make : paper, rayon, cellophane 4. Thylakoids in stacks (Grana) a. Rather than as simple bands b. Thylakoids are membranes inside chloroplast containing chlorophylly Features of Streptophytes - Charophytes o Mostly green algae like o Closet relative to land plants ▪ Evidence 1. Both nuclear and chloroplast DNA 2. Anatomical structure ▪ A type of “green alga” o Land plants are not descended from modern charophytes, but share a common ancestor with modern charophytes - Embryophytes o Land plants Features of streptophytes (Charophytes and land plants) 1. Cell plate and phragmoplast a. a plant-specific structure that helps divide plant cells by forming a new cell wall between the two daughter cells b. divides by middle outwards ▪ Microtubules and associated proteins guiding formation of cell plate 2. Plasmodesmata o Extension of cell membrane through pores of cell wall 3. Sperm structure 4. Peroxisome enzymes 5. Rose-shaped cellulose- synthesizing complexes a. In cell membrane 6. Sporopollenin a. Durable polymer preventing the zygote from drying out b. Found in the walls of: i. Plant spores ii. Pollen c. Chemically inert (a substance is not reactive to other substances, especially oxidation) i. Stable ii. Persists in environment d. Protects from desiccation, decay The move to land: potential advantages - Air filters less sunlight than water o There is more light for photosynthesis - Air has more CO2 than water o There Is more fuel for photosynthesis - Early terrestrial habitats lacked pathogens or predators/herbivores - Terrestrial soil is richer in nutrients than aquatic soil Land plants Embryophytes live in dry environments Features of Embryophytes/land plants 1. Cuticle-waxy covering 2. Multicellular, Jacketed sex organs a. Gametangia = makes sperm or eggs 3. Embryophyte condition a. Zygote (2n/diploid) retained in maternal tissue (n/haploid) i. Egg stays on mom ii. Zygote develops into an Embryo 4. Alternation of generations a. All Sexual reproduction i. b. Alternation of generations i. Gametangia Antheridium - male sex organs - produces sperm - haploid Archegonium - Female sex organ - Produces egg - Haploid Alternation of generations (continued) - MULTICELLULAR haploid & diploid stages - Arose independently in evolution several (or many) times—so also in other groups o The alternating “generations” are: ▪ Gametophyte (haploid, 1n): makes gametes ▪ Sporophyte (diploid, 2n): makes spores Life cycles a. Animals b. Land plants Spore - Single cell that can divide to produce a multicellular organism o Often with protective coat - Produced by meiosis Gamete - Single cell that can unite with another gamete to produce a diploid zygote Green alga without alternation of generations - Most of life as a single cell haploid Alternations multicellular Sporophyte = multicellular diploid (2n) - Formed from fertilization - Produced from zygote o Mitosis  - Produces haploid spores through meiosis o Haploid spores sprout to form gametophyte - Make spores Spores - haploid Gametophytes = multicellular haploid (n) - Produce from sprouting spores - Produces egg and sperm o Fuse to form zygote - Gametophytes make gametes There are 10 divisions (phyla) of land plants 4 major land plant divisions 1. Mosses 2. Ferns 3. Conifers 4. Angiosperms Division Bryophyta (Mosses) - Major features o 15 000 species o Low growing o Confined to damp areas ▪ Swimming sperm o No true vascular tissue / (rudimentary vascular system) ▪ No water transport system ▪ No true roots o No true leaves - Life cycle o Dominated by gametophyte stage (haploid) o Spores for reproduction ▪ Haploid cells which sprout to form gametophyte o Homosporous = 1 spore size 1. Spores (n) 2. Germinates 3. Gametophyte a. Archegonium b. Antheridia 4. Water drops carries sperm to archegonia 5. Fertilization within archegonium 6. Zygote (2n) 7. Embryo 8. Sporophyte a. Sporangium i. Vessel that makes spores 9. Meiosis to make spores Archegonia Antheridia Next major step in evolution vascular tissue - Vascular tissue o support and supply o xylem o phloem Division Pterophyta (Ferns, Horsetails) - Major features o 20 000 species o Appeared 400 mya o Vascular ▪ Water transport system ▪ Xylem, phloem, roots, leaves. Support and supply o Motile sperm o Homospory or heterospory ▪ 1 size of spore from meiosis ▪ 2 sizes od spore from meiosis - Life cycle o Dominated by sporophyte stage (diploid) o Fragile gametophyte 1. Spore 2. Germinates 3. Gametophyte a. Is heart shaped b. 1 cell thick c. Co-sex d. 4. Water droplet moves sperm to egg 5. Fertilization 6. Zygote (2n) 7. Embryo 8. Sporophyte a. Gametophyte stays for a moment b. Sporangium i. Sorus 1. Group of sporangium 9. Meiosis to make spores 5 divisions (phyla) of seed plants 1. Coniferphyta 2. Anthophyta Seed plants have both seeds and pollen - Seed plants have both seeds and pollen Seeds - Embryo + nutrition + seed coat - Develops from ovule o Novel structure appearing in seed plants o Site of female meiosis o Contains female gametophyte, female sex organs, egg and embryo o Site of reproduction Pollen - Pollen grain is mature male gametophyte - Few cells in size Ovule (conifer) at early stage – just before meiosis in megasporangium Micropyle - a small opening in the surface of an ovule, through which the pollen tube penetrates, Integument (2n) - a layer of sporophyte tissue - 1 layer in conifers - 2 layers in angiosperms Megasporangium (2n) = nucellus - Megasporangium -> meiosis -> 4 megaspores ( 3 die and 1 megaspore devlopes into megagametophyte) --> egg The ovule becomes the seed after fertilization Division Coniferophyta (the Conifers) - 550 species - Reproductive organs in cones - Sporophyte dominant - Heterosporous - Microgametophyte o pollen - megagametophyte o within ovule o makes egg and then nourishes embryo example - white pine o 5 leaves in each group - Larch, tamarack - Bald cypress Life cycle 1. Ovulated cone 2. An ovulate cone scale has 2 ovules each containing a megasporangium 3. Pollination occurs when a Pollen grain reaches the ovule a. the pollen grain then germinates forming a pollen tube that slowly digests its way through the megasporangium 4. While the pollen tube develops the megasporeacyte undergoes meiosis producing 4 haploid cells one survives as a megaspore 5. the megaspore develops into a female gametophyte that contains two or three archegonia a. Each of which will form an egg 6. by the time the egg armature sperm cells have developed in the pollen tube which extends to the female gametophytes a. fertilization occurs when sperm and egg nuclei unite 7. fertilization usually occurs more than a year after pollination all eggs may be fertilized but usually only one zygote develops into an embryo the ovule becomes a seed consisting of an embryo food supply and seed coat Summary - Seeds and pollen - Cones o Male and female - Naked seeds - Gymnosperms = naked seeds - Seed o Embryo nourished by megagametophyte - Slow reproduction o Jack pine Angiosperms Adaptations 1. Flower - Flower o In an angiosperm, a specialized shoot with up to four sets of modified leaves, bearing structures that function in sexual reproduction. - Sepal o modified leaf in angiosperms that helps enclose and protect a flower bud before it opens. - Petals o A modified leaf of a flowering plant. Petals are the often colourful parts of a flower that advertise it to insects and other pollinators. - Stamen o The pollen-producing reproductive organ of a flower, consisting of an anther and a filament. o Macrosporophylls ▪ They produce microspores that develop into pollen grains containing male gametophytes - Anther o In an angiosperm, the terminal pollen sac of a stamen, where pollen grains containing sperm-producing male gametophytes form - Filament o In an angiosperm, the stalk portion of the stamen, the pollen-producing reproductive organ of a flower. - Carpels o The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary. ▪ Megasporophylls They produce megaspores that gave rise to female gametophytes  o Single carpel = pistil - Stigma o The sticky part of a flower’s carpel, which receives pollen grains. - Style o The stalk of a flower’s carpel, with the ovary at the base and the stigma at the top. - Ovary o In flowers, the portion of a carpel in which the egg-containing ovules develop. o  2. Fruit Fruit - Has a seed develops from ovules after fertilization the ovary wall thickens and the ovary matures into a fruit - Protect seeds and aid in their dispersal Cell cycle 1. In the megasporangium of each ovule the megaspore site divides by meiosis producing 4 megaspores a. one survives and gives rise to the female gametophytes 2. on the anther each microsporangium contains microsporocytes that divide by meiosis producing microspores 3. A microspore develops into a pollen grain the generative cell of the gametophytes will divide forming 2 sperm a. the tube cell will produce the pollen tube 4. After pollination eventually 2 sperm cells are discharged in each ovule 5. double fertilization occurs one sperm fertilizes the egg forming the zygote a. The other sperm fertilizes the central so forming the endosperm i. a food supply ii. triploid cell 6. the zygote develops an embryo that is packaged along with food into a seed 7. When a seed germinates the embryo develops into a mature sporophyte a. Containing a rudimentary root and one or two seed leaves called cotyledon 8. The triploid Central cell of the female gametophytes develops into that endosperm  a. tissue rich in starch another food reserves that nourish the developing embryo - Self-pollination - Cross-pollination - Ovaries ripen into fruits which often carry seeds by wind water or animals to new locations Angiosperm diversity Monocot - 1 cotyledon Dicot - 2 cotyledons Plant hierarchical organization Roots - Organ that anchors a vascular plant in the soil - Absorbs minerals and water - Stores carbohydrates Lateral roots - Branch from primary/first root - Enhancing the ability of the root system to anchor - And increase water and mineral absorption Tap root - Tall erect plants with large shoot - Developed from primary root Root hairs - Send finger like extensions of root epidermal cells, emerged an increase the surface area of root enormously Stem - Is an organ that raises and separates leaves, exposing them to sunlight - Facilitate dispersal of pollen and fruit Consist - Nodes o the point at which leaves are attached - internodes o the stem segments between nodes - apical bud o A type of bud found in shoots - Axillary bud o In the upper angle form by each leaf and stem Leaves - Most vascular plant - Main photosynthetic area  - gas exchange - dissipate heat - defending themselves from herbivores and pathogens consist of… 1. flatten blade 2. petiole = stalk 3. veins a. Vascular tissue of leaves Dermal, vascular and ground plant tissue Dermal tissue - Is the plant's outer protective covering Epidermis - In non woody and very young parts of woody plants - Guard cells o Gaseous exchange - Trichomes o Reduce water loss o Reflect sunlight Cuticle - In leaves and most stems Periderm - In woody plants Vascular tissue - Carries out long distant transport of materials between the root and shoot systems - provides mechanical support 1. xylem a. Conducts water and dissolved minerals upwards from roots into the shoots 2. phloem a. transports sugars the product of photosynthesis from where they are made (leafs) to where they're needed (roots and sites of growth) - Collectively called stele Ground tissue - Filter, storge, photosynthesis and support by different specialized cells - Internal to the vascular tissue known as pith - External to the vascular tissue is known as cortex Different meristems generate cells for primary and secondary growth - Indeterminate growth o Plant grows throught its life - Meristems o Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth. 1. Apical meristems a. Located at the tips of the roots and shoots b. In axillary buds of shoots c. Primary growth i. Allows roots to extend through the soil ii. Allows shoots to increase their exposure to light 2. Lateral meristems  a. Secondary growth b. Vascular cambium i. Adds layers of vascular tissues (wood) and secondary phloem c. Cork cambium i. Replaces epidermis with the thicker, tougher periderm d. Apical dominance Stem Growth and anatomy Leaf anatomy Leaf primordia Stomata - Which allows exchange of CO2 and O2 between the surrounding air and the photosynthetic cells inside the leaf - Regulates CO2 uptake Mesophyll - Leaves ground tissue - Cells for photosynthesis - 2 distinctive layers o Palisade mesophyll o Spongy mesophyll Secondary growth increases the diameter of stems and roots in woody plants 1. Primary growth from the activity of the apical meristem is nearing completion. The vascular cambium has just formed. 2. Although primary growth continues in the apical bud, only secondary growth occurs in this region. The stem thickens as the vascular cambium forms secondary xylem to the inside and secondary phloem to the outside. 3. Some initials of the vascular cambium give rise to vascular rays 4. As the vascular cambium’s diameter increases, the secondary phloem and other tissues external to the cambium can’t keep pace because their cells no longer divide. As a result, these tissues, including the epidermis, will eventually rupture. A second lateral meristem, the cork cambium, develops from parenchyma cells in the cortex. The cork cambium produces cork cells, which replace the epidermis. 5. In year 2 of secondary growth, the vascular cambium produces more secondary xylem and phloem, and the cork cambium produces more cork. 6. As the stem’s diameter increases, the outermost tissues exterior to the cork cambium rupture and are sloughed off. 7. In many cases, the cork cambium re-forms deeper in the cortex. When none of the cortex is left, the cambium develops from phloem parenchyma cells. 8. Each cork cambium and the tissues it produces form a layer of periderm. 9. Bark consists of all tissues exterior to the vascular cambium