KEY CONCEPT Plant life began in the water and became adapted to land.
Land plants evolved from green algae. Plants and green algae have many common traits. both are photosynthetic eukaryotes both have the same types of chlorophyll both use starch as a storage product both have cell walls with cellulose
Genetic analysis points to the common ancestor of all plants. extinct green algae species in class Charophyceae modern charophyceans common in lakes and ponds
Important plant characteristics likely originated in charophyceans. multicellular body allowing for specialization of cells and tissues cell division that allows for chemical communication between cells reproduction involving sperm swimming to egg
True plants evolved through natural selection. Ancestral charophyceans lived in areas of shallow water. Those that could survive longer dry periods were favored. First true plants probably grew at edges of water. True plants have embryos that develop while attached to female parent.
True plants evolved through natural selection.
Plants have adaptations that allow them to live on land. Challenges of living on land have selected for certain plant adaptations. A cuticle allows plants to retain moisture. waxy, waterproof layer holds moisture in
Stomata are tiny holes in the cuticle. can open and close allow air to move in and out
collection of specialized tissues A vascular system allows resources to move to different parts of the plant. collection of specialized tissues brings water and mineral nutrients up from roots disperses sugars from the leaves allows plants to grow higher off the ground sugars water and mineral nutrients
Lignin allows plants to grow upright. plant cells lignin hardens cell walls of some vascular tissues provides stiffness to stems
Pollen grains allow for reproduction without free-standing water. pollen grains contain a cell that divides to form sperm pollen can be carried by wind or animals to female structures
A seed is a storage device for a plant embryo. seed coats protect embryos from drying wind and sunlight embryo develops when environment is favorable
Plants evolve with other organisms in their environment. Plants and other organisms can share a mutualistic relationship. a mutualism is an interaction in which two species benefit plant roots and certain fungi and bacteria flowering plants and their animal pollinators
Plants have adaptations that prevent animals from eating them. spines and thorns defensive chemicals