Plants Study Guide (High School)
20.1
KEY CONCEPT-Plant life began in the water and became adapted to land.
Plants are multicellular eukaryotes, most of which produce their own food through photosynthesis and have adapted to life on land. Plants share many characteristics with green algae. Both are photosynthetic eukaryotes with the same types of chlorophyll. Both also use starch as a storage product and have cell walls that contain cellulose.
One ancient species of green algae is the common ancestor of all plants. If it were alive today, it would be classified as a charophycean. Natural selection likely favored individuals of the ancestral charophycean species that could withstand dry periods, until eventually the first true plant species evolved.
Life on land presents different challenges from life in the water. These challenges have acted as selective pressures for plant life on Earth.
• Retaining moisture: A cuticle is a waxy, waterproof layer that helps hold in moisture. Tiny holes in the cuticle, called stomata, can open and close allowing air to move in and out.
• Transporting resources: A vascular system is a collection of specialized tissues that bring water and mineral nutrients up from plant roots and disperse sugars down from the leaves.
• Growing upright: Lignin is a material that hardens the cell walls of some tissues, providing structure for plants to grow upright and space for vascular tissue.
• Reproducing on land: A pollen grain is a two-celled structure produced by seed plants that contains a cell that will divide to form sperm. Pollen can be carried by wind or animals to female reproductive structures. A seed is a storage device that also protects and nourishes a plant embryo.
Plants evolve with other organisms in their environment.
• A mutualism is an interaction between two species in which both species benefit. Important mutualisms involving plants include those between plant roots and certain fungi and bacteria, and those between plants and their animal
KEY CONCEPT-Plant life began in the water and became adapted to land.
Plants are multicellular eukaryotes, most of which produce their own food through photosynthesis and have adapted to life on land. Plants share many characteristics with green algae. Both are photosynthetic eukaryotes with the same types of chlorophyll. Both also use starch as a storage product and have cell walls that contain cellulose.
One ancient species of green algae is the common ancestor of all plants. If it were alive today, it would be classified as a charophycean. Natural selection likely favored individuals of the ancestral charophycean species that could withstand dry periods, until eventually the first true plant species evolved.
Life on land presents different challenges from life in the water. These challenges have acted as selective pressures for plant life on Earth.
• Retaining moisture: A cuticle is a waxy, waterproof layer that helps hold in moisture. Tiny holes in the cuticle, called stomata, can open and close allowing air to move in and out.
• Transporting resources: A vascular system is a collection of specialized tissues that bring water and mineral nutrients up from plant roots and disperse sugars down from the leaves.
• Growing upright: Lignin is a material that hardens the cell walls of some tissues, providing structure for plants to grow upright and space for vascular tissue.
• Reproducing on land: A pollen grain is a two-celled structure produced by seed plants that contains a cell that will divide to form sperm. Pollen can be carried by wind or animals to female reproductive structures. A seed is a storage device that also protects and nourishes a plant embryo.
Plants evolve with other organisms in their environment.
• A mutualism is an interaction between two species in which both species benefit. Important mutualisms involving plants include those between plant roots and certain fungi and bacteria, and those between plants and their animal