Plant and Animal Nutrition
Plant Nutrition
Bryophyte Nutrition
Seedless plants are small and have a thallus organization. Although they have colonized the terrestrial environment, they lack true roots for water and mineral absorption, and vascular tissue for transport.
Cormophyte Nutrition Process
- Absorption of water and minerals by roots (root hairs are coated in a piliferous layer).
- Transportation of xylem sap.
- Gas exchange (carbon dioxide and oxygen).
- Transportation of phloem sap.
Xylem Transport
Water and mineral salts enter the xylem. Xylem transport occurs through:
- Transpiration (water vapor loss through leaf and stem stomata).
- Cohesion of water molecules (due to hydrogen bonds).
- Root pressure (nutrient uptake due to concentration differences between soil and root cells).
Gas exchange of oxygen and carbon dioxide occurs through stomata (abundant on leaf undersides) and lenticels (openings in the epidermis of woody stems) and root hairs (outgrowths of epidermal cells).
Phloem Transport
Phloem transports sugars and amino acids (translocation). Sap moves from source areas to sink areas, explained by the pressure flow hypothesis.
Plant Excretion and Secretion
Excretion is the removal of unusable substances that hinder metabolism (e.g., leaf loss). Secretion is the removal of useful substances (e.g., nectar).
Plant Hormones
Plant hormones (auxins, gibberellins, cytokinins, abscisic acid, and ethylene) are chemicals produced by specialized cells that affect other cells. They promote, inhibit, or modify plant development.
Plant Movements
Tropisms are permanent growth movements in response to a stimulus (positive or negative). Examples include phototropism, hydrotropism, thigmotropism, chemotropism, and geotropism. Nastic movements are not determined by stimulus direction but by organ constitution (e.g., photonasty, thermonasty, thigmonasty).
Plant Reproduction
Asexual Reproduction
Asexual reproduction involves one parent and no gamete fusion. Plants reproduce vegetatively through rhizomes, tubers, bulbs, and stolons.
Sexual Reproduction
Sexual reproduction involves two individuals contributing gametes. Gametes are formed in gametangia (uni- or multicellular). Female gametangia are oogonia (bryophytes and pteridophytes) and archegonia (bryophytes and pteridophytes). Male gametangia are antheridia (bryophytes and ferns).
Moss Life Cycle
Antheridia produce biflagellate male gametes. Archegonia produce female gametes (oospheres). Sporogenous cells undergo meiosis, producing haploid spores. Spores germinate to form a protonema.
Fern Life Cycle
Ferns have an underground rhizome with fronds. Sporangia (in sori) on the underside of fronds undergo meiosis, producing spores. Spores germinate into a prothallium.
Flower Structure
Flowers can be fertile or sterile. A flower consists of a stalk, thalamus (floral receptacle), and whorls of parts.
Sterile Parts
- Sepals (calyx)
- Petals (corolla)
Fertile Parts
- Androecium (stamens)
- Gynoecium (carpels: ovary, style, stigma)
Pollination and Fertilization
Pollination is the transfer of pollen grains to the stigma. Self-pollination occurs within a flower; cross-pollination occurs between different plants. Pollination types include anemophily, zoophily, and hydrophily.
Fertilization begins when the pollen grain reaches the stigma and germinates, producing a pollen tube. The pollen tube grows to the oosphere, where fertilization occurs, forming a zygote.
Embryo and Seed Formation
The zygote develops into an embryo. In dicots, two cotyledons form, and the embryo becomes heart-shaped.
Animal Nutrition
Main Exchange Surfaces
- Gastrointestinal tract (nutrient absorption)
- Respiratory surface (gas exchange)
- Excretory surface (waste removal)
Nutrition Process
- Ingestion (food uptake)
- Digestion (mechanical and chemical breakdown)
- Circulation (nutrient distribution)
- Excretion (waste removal)
Digestion
Digestion is the mechanical and chemical breakdown of food. Types include intracellular, extracellular, and mixed.
Mechanical Digestion
Mechanical digestion involves food fragmentation and bolus movement through the alimentary canal (peristalsis).
Chemical Digestion
Chemical digestion involves the hydrolysis of food macromolecules by digestive enzymes and bile, releasing small molecules for absorption.
Parts of the Digestive Tract
Mouth
- Food fragmentation
- Chemical digestion (carbohydrates)
- Lubrication (saliva)
- Swallowing
Esophagus
Connects the mouth and stomach; may have a crop.
Stomach
Stores food, regulates flow to the intestine, and performs digestion. Chyme is formed by mixing food with gastric juices.
Small Intestine
(Duodenum, jejunum, ileum) Performs most chemical digestion and nutrient absorption.
Large Intestine
(Cecum, colon, rectum) Absorbs water and ions; forms feces.