20.1 Origins of Plant Life
20.1 Origins of Plant Life
Bell Ringer
• Read the info on p611, then answer the following questions. • 1-Based on the question on page 611, what form do you think this domination takes? • 2-What are some important plants in the US? • 3-What value do other plants have? 20.1 Origins of Plant Life
KEY CONCEPT Plant life began in the water and became adapted to land. 20.1 Origins of Plant Life
Land plants evolved from green algae.
• Green algae is a photosynthetic eukaryote • It is a plant like protist • It has pigments that give various types of algae their distinct colors 20.1 Origins of Plant Life • 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 20.1 Origins of Plant Life
• Genetic analysis points to the common ancestor of all plants. – extinct green algae species in class Charophyceae – modern charophyceans common in freshwater habitats like lakes and ponds. 20.1 Origins of Plant Life
Question
• What evidence suggests that green algae are close relatives of land plants? 20.1 Origins of Plant Life
Bell Ringer
• Look at figure 20.2 on page 613. Answer the following questions: • 1-What is the common ancestor of all plants? • 2-What is the first category of plants to evolve from the ancestral line (in # 1) • 3-When did the flowering plant lineage diverge from the cone-bearing plant lineage? 20.1 Origins of Plant Life
• 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 20.1 Origins of Plant Life
– Ancestral charophyceans lived in areas of shallow water. – Those that could survive longer dry periods were favored. – Like mosses they relied on droplets of water that brought sperm to eggs to produce the next generation. – Also have a simple structure similar to that of moss, keeping low to the ground to retain moisture 20.1 Origins of Plant Life
-First true plants probably grew at edges of water.
-True plants have embryos that develop while attached to female parent. 20.1 Origins of Plant Life
• True plants evolved through natural selection. 20.1 Origins of Plant Life
• Challenges of living on land have selected for certain plant adaptations. • Unlike land plants algae are constantly surrounded by water. – Needed for photosynthesis – Buoyancy supports weight – Allow reproduction and dispersal – Prevents from drying out 20.1 Origins of Plant Life
Plants have adaptations that allow them to live on land. • A cuticle allows plants to retain moisture. – waxy, waterproof layer – holds moisture in 20.1 Origins of Plant Life
• Stomata are tiny holes in the cuticle.
stoma
– can open and close – allow air to move in and out Without stomata movement of air would be prevented by the cuticle 20.1 Origins of Plant Life
• 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
water and mineral nutrients
sugars 20.1 Origins of Plant Life
• Lignin allows plants to grow upright.
lignin
plant cells
– hardens cell walls of some vascular tissues – provides stiffness to stems – Allows plants to retain upright structure 20.1 Origins of Plant Life
• Plant height is limited by the ability of a plant to support it’s own weight. 20.1 Origins of Plant Life
• Pollen and seeds are adaptations that allow seed plants to reproduce completely free of water. 20.1 Origins of Plant Life
• 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 20.1 Origins of Plant Life
• 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 20.1 Origins of Plant Life
Bell Ringer
• Some scientist think that certain species of green algae should be in the kingdom Plantae. What reasons might these scientist use to defend their position? • Do you agree or disagree? Why? 20.1 Origins of Plant Life
Plants evolve with other organisms in their environment.
• Plants have coevolved with other terrestrial organisms for millions of years • Some of these relationships are cooperative while others have evolved between plants species and the animals that eat them. 20.1 Origins of Plant Life
• 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 - Ex: hawk mouth and orchid 20.1 Origins of Plant Life
• Plants have adaptations that prevent animals from eating them. – spines and thorns – Ex: Roses, cactus 20.1 Origins of Plant Life
Plants have adaptations that prevent animals from eating them. •Chemicals – Some insects use defensive chemicals produced by plants to their advantage. - Ex: larvae of monarch butterflies feed exclusively on milkweed species. Milkweed plants produce a chemical that makes monarch larvae, adults, and even eggs taste bad to potential predators. 20.1 Origins of Plant Life
Question
• What do pollen and seeds allow plants to do on land? 20.1 Origins of Plant Life
• What do stomata and cuticles allow plants to do? 20.1 Origins of Plant Life
• What does lignin help plants do? 20.1 Origins of Plant Life
• What does a vascular system allow plants to do?