Create a Plant Evolution Timeline Task: In groups, use the pictures to create a timeline that depicts the evolution of plants using the cards provided. Write the order in your bellringer section. TRY YOUR BEST!!! Do not write on these cards – they are class sets.

Plant Evolution

Origin of Land Plants Land plants evolved from primitive green algae around 475 million years ago. In a relatively short time of about 50 million years, plant diversified abundantly and colonized many land areas. Today, with more than 250,000 species, they are second in size only to the insects. We now know that plants, like all living organisms, had aquatic ancestors. A specific group of freshwater green algae are the closest relatives to the land plants.

Major Events in Plant Evolution There are four major events for plant life history: Water to land (aquatic to terrestrial) Developed vascular tissue Seeds produced Flower production Groups are distinguished from algae by reproduction (life cycle) that involves the development of a multi-cellular embryo attached to the mother plant for its protection and nourishment. This is why terrestrial plants are also called embryophytes.

Why did plants transition to land? What are the limiting factors for aquatic plants? Nutrients - Open bodies of water tend to be deficient of nutrients. Higher concentration of nutrients at the shoreline. Light – Light does not penetrate very far through water. Over 90 percent of the entire ocean area on Earth—is called the aphotic zone, where no light is present Advantages of transitioning to land:  light intensity  concentration of nutrients CO2 higher in air than water

What problems do land organisms face? The biggest challenge plants faced when moving to land was water deficits. Danger of desiccation (drying out) required new adaptations: transport tissue, cuticle, etc.

Overview of Plant Evolution Charophytes: Ancestral Green Algae Bryophytes Ferns & allies Gymnosperms Angiosperms Flowers Seeds Overview of Plant Evolution Vascular tissue Cuticles

Charophytes 2. Chara, a green alga. Charophytes, a group of fresh water green algae, are the closest relatives to the land plants. Green algae differ from plants in many ways. they don't have a specialized transport or support systems. green algae do not have true leaves green algae lack cuticles (a waxy layer on the outer wall of epidermal cells) and stomata (specialized cells for gas exchange). Like the land plants, green algae contain two forms of chlorophyll (a and b), which they use to capture light energy to make sugars Green algae differ from plants in many ways. Because they live in the water, they don't have a specialized transport or support systems. Their bodies are supported by the water, and almost all of the cells photosynthesize and have access to the nutrients present in the water. Therefore, transport of nutrients is not necessary. Even though they photosynthesize, green algae do not have true leaves (which are characterized by the presence of vascular tissue). Additionally, green algae lack cuticles (a waxy layer on the outer wall of epidermal cells) and stomata (specialized cells for gas exchange). 2. Chara, a green alga.

Main Groups of Land Plants The four main groups of land plants are primarily determined by the major plant evolution events. Bryophytes Pteridophytes Gymnosperms Angiosperms

Characteristics of Land Plants Bryophytes Most primitive, no vascular tissue, low growing, live in moist environments, ex. mosses Pteridophytes Seedless plants, has vascular tissue, ex. ferns Gymnosperms Early seed plants, have naked seeds, has vascular tissue, ex. conifers Angiosperms Seeds protected by growing in ovaries, flowering plants, has vascular tissue, most modern and diverse

Bryophytes (The mosses, liverworts and hornworts) Bryophytes don't receive as much attention as flowering plants, ferns, or conifers because most bryophytes are small and inconspicuous. They have no vascular tissue (no true xylem or phloem) to lend them structural support, nor do they have true leaves or showy flowers. This does not mean that bryophytes are not important; mosses in particular, play important roles in prevention erosion along and insulating the arctic permafrost.

Introduction to the Pterophyta (The ferns) The ferns are an ancient lineage of plants, at least to the Devonian Period. There are approximately 11,000 species of ferns; the second largest group of plants. Ferns and other Pterophytes lacked seeds, a condition still represented by ferns (and a few other groups not discussed here). The second major lineage of land plants to evolve is referred to as the seedless, vascular plants. Even though ferns have free living gametophytes, the sporophyte is the dominant phase of the fern life cycle. Ferns produce spores (not seeds) 9. Fiddle head of new fern frond 10. Spores on the back of a fern frond

Introduction to Gymnosperms The gymnosperms formed vast forests that dominated the landscape for more than 200 million years. The pine tree, a representative gymnosperm, is a sporophyte. The gametophyte generation develops from spores that are produced in male and female cones. The pollen (male gametophyte) is transferred to the ovule (female gametophyte) via wind. After fertilization, the seed begins to develop. The entire process, from cone production to seed production, can take up to three years. 11. A pine with female cones

Introduction to Angiosperms: The emergence of the flower Today, the flowering plants are by far the most diverse and geographically widespread of all plants The angiosperms arose during the early Cretaceous period about 130 mya. The main feature that led to their success was the evolution of flowers and fruits. The flower is reproductive structure that bears seeds within protective chambers called ovaries. The presence of the ovary is one of the major differences between angiosperms and the gymnosperms. The ovary develops into the fruit, which is an important structure for seed dispersal. Flowers also allow for specialized pollination by attracting and rewarding pollinators. 12. A bee pollinating a flower

Create a Plant Evolution Timeline Task: Now, use the pictures and resources to create a timeline that depicts the evolution of plants using the cards provided. Under Exit Slip, Re-write the order and explain why you put each card in its location. Do not write on these cards – they are class sets.