Plant Diversity and Life Cycles Chapter 23
What is a Plant? • Plants are multicellular eukaryotes whose cells have cell walls. • Most plants are autotrophs, meaning they produce their own food through photosynthesis.
Establishment of Land Plants • In order to thrive on land, plants had to be able to absorb nutrients from their surroundings, to have survive dehydration or avoid drying out, and to have a way of dispersal – or way of scattering- that did not require water.
Absorbing Nutrients • On land, most vascular plants absorb nutrients from the soil through their roots. • Symbiotic relationships between fungi and plant roots are called mycorrhizae.
Preventing Water Loss • A watertight covering, which reduces water loss, made it possible for plants to live in dry habitats. • Cuticle – a waxy or fatty and watertight layer on the external wall of epidermal cells. • Roots obtain water from the soil and allow vascular plants to replace water lost to the atmosphere.
Dispersal on Land • Aquatic algae release cells that undergo dispersal by drifting in water currents or by active swimming. • Spore – a reproductive cell or multicellular structure that is resistant to environmental conditions. • Seed plants produce a special kind of spore called pollen that is scattered across the land by wind or by animals. • Pollen transports sperm cells to eggs.
Plant Life Cycles • Plants have life cycles in which haploid gametophytes alternate with diploid sporophytes. • A life cycle in which a gametophyte alternates with a sporophyte is called alternation of generations. • Sporophyte – in plants and algae that have alternation of generations, the diploid individual or generation that produces haploid spores. • Gametophyte – in alternation of generations, the phase in which gametes are formed, a haploid individual that produces gametes.
Assignment • Pg. 546, 1-5 • Write out the question and the answer to these.