evolution of plants

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Evolution of plant life:

Evolution of plant life

Introduction to the Green Plants :

Introduction to the Green Plants Land plants first appeared in the Ordovician (~460 million years ago) but did not begin to resemble modern plants until the Late Silurian.

Introduction to the Green Algae:

Introduction to the Green Algae The Charophyceae, a group of fresh water green algae, are the closest relatives to the land plants. Like the land plants, green algae contain two forms of chlorophyll (a and b), which they use to capture light energy to make sugars that are stored as starch inside plastids (specialized organelles).

Early land plants :

Early land plants The early land plants, represented today by the bryophytes (mosses, liverworts, and hornworts), possessed two important features that allowed them to live on land: 1) a waxy cuticle to protect against desiccation (drying out) and 2) protection of gametes and embryos in a protective jacket made of cells.

Introduction to the Bryophyta (The mosses, liverworts and hornworts) :

Introduction to the Bryophyta (The mosses, liverworts and hornworts) After flowering plants and ferns, mosses are the most diverse group of plants, with more than 10,000 species in 700 genera. This makes mosses almost twice as diverse as mammals. 3. A moss. 4. A liverwort.

Introduction to the Bryophyta, continued :

Introduction to the Bryophyta, continued The earliest land plants were probably very similar to modern-day bryophytes. In bryophytes, the gametophytes are nutritionally independent of the sporophytes.

The second major period of plant evolution: The diversification of vascular plants:

The second major period of plant evolution: The diversification of vascular plants Relatively early in the history of plants, the evolution of efficient fluid-conducting systems, consisting of xylem and phloem , .

Introduction to the Lycophyta (Club mosses and scale trees) :

Introduction to the Lycophyta (Club mosses and scale trees) The lycophytes are a small and inconspicuous group of plants today, but in the Carboniferous some lycophytes were forest-forming trees more than 35 meters tall.

Introduction to the Pterophyta (The ferns) :

Introduction to the Pterophyta (The ferns) Even though ferns have free living gametophytes , the sporophyte is the dominant phase of the fern life cycle. Ferns produce spores (not seeds ) that are borne on megaphylls (often called fronds).

The third major period of plant evolution: The origin of the seed :

The third major period of plant evolution: The origin of the seed The seed , a specialized unit of reproduction, advanced the colonization of land by further providing a food source for the plant embryo and protecting it from harsh conditions. Seeds are also an important unit of dispersal (replacing the spore as the stage of the life cycle that disperses offspring).

Introduction to the Gymnosperms :

Introduction to the Gymnosperms The gymnosperms descended from a group of Devonian plants, the progymnosperms. They coexisted with the bryophytes, ferns, and other seedless vascular plants, but their adaptive radiation occurred during the Carboniferous and early Permian.

The fourth major episode in the evolutionary history of plants: The emergence of the flower :

The fourth major episode in the evolutionary history of plants: The emergence of the flower 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 a complex reproductive structure that bears seeds within protective chambers called ovaries. 12. The parts of a flower

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