G12 Bio L22.1 Notes PDF

Name: Class/ Section: 12 Date: Chapter:22 Intro. to plants Lesson: 22.1 What is a palnt Textbook p.:634 - 638 Class Notes 22.1 What Is a Plant? Kingdom Plantae...

Name: Class/ Section: 12 Date: Chapter:22 Intro. to plants Lesson: 22.1 What is a palnt Textbook p.:634 - 638 Class Notes 22.1 What Is a Plant? Kingdom Plantae Plants are eukaryotes that have cell walls containing cellulose and carry out photosynthesis using chlorophyll a and b within the chloroplasts.. Characteristics of Plants Plants are eukaryotes that have cell walls containing cellulose. Mostly autotrophs, plants use chlorophyll a and b to carry out photosynthesis. Without moving about, plants get what they need from the environment.  Sunlight: gathered by leaves by chlorophyll in chloroplast that are arranged in ways that maximizes absorption of light for photosynthesis.  Gas exchange: brings in oxygen and carbon dioxide and releases excess oxygen  Oxygen is needed for their cellular respiration to release energy  Carbon diooxide is needed for photosymthesis.  Water: absorbed mostly from the soil and transported internally – needed for photosynthesis.  Minerals: absorbed along with water from the soil. The History and Evolution of Plants Ancestors of today’s land plants were water-dwellers similar to today’s green algae. Over time, the demands of life on land favored the evolution of plants that: 1. Are more resistant to the drying rays of the sun 2. Are more capable of conserving water 3. Are more capable of reproducing without water. 1 The first land plants were dependent on water and lacked leaves and roots. Five major groups of plants are classified based on four important features (derived characters)  embryo formation  specialized water-conducting tissues  seeds  flowers The Plant Life Cycle The life cycle of land plants has two alternating phases, a diploid (2N) phase and a haploid (N) phase. This shift between haploid and diploid is known as the alternation of generations. Sporophyte: the multicellular diploid phase, a spore-producing plant Gametophyte: the multicellular haploid phase, a gamete-producing plant. Trends in Plant Evolution The trend shows that the gametophyte (2N) reduces and the sporophyte increases. Green algae: gametophytes is dominant, some green algae have sporophyte phase. Mosses and their relatives consist of a relatively large gametophyte and smaller sporophytes. Ferns and their relatives have a small gametophyte and a larger sporophyte. Seed plants have an even smaller gametophyte than ferns, which is contained within sporophyte tissues. 2