3.1 From Algae to Terrestrial Plants

Agenda Lesson 3.1 From Algae to Terrestrial Plant Read text pages Answer Learning Check #1-6 on page 93 Work on Dichotomous Key Assignment

Learning Goals Students will discuss the link between plant-like protists and the plant kingdom. Students will state how algae are classified Students will list the differentiate between plants and algae. Students will list the evolutionary changes that allowed the transfer to land.

From Algae to Terrestrial Plants Scientists do agree that plants evolved from algae. They have been on the earth for about 2 billion years and scientists are still discovering new species They do not agree however whether they should be classified in the Kingdom Protista or Plantae. Simple, aquatic, plant-like organisms that contain chlorophyll Lack the leaves, roots, stems and water-conducting materials of plants Range in size (single cells to giant seaweeds 60 m in length)

The Multicellular Algae Algae are classified into six different phyla based on the type of chloroplasts and pigments they contain. Have different types of chlorophylls and other pigments, suggests that chloroplast-containing cells evolved three times. Three phyla are unicellular – Dinoflagellates – Diatoms – Euglenoids three are multi-cellular seaweeds Seaweeds are large multicellular algae. Divided into 3 main groups based on their colour. – Green, red and brown algae Other differences include the chemistry of their cell walls, the number and position of flagella (if any) and the form that food reserves take in their cells.

Dinoflagellates (Pyrrophytes) Red algae (Rodophytes) Brown algae (Phaeophytes) Diatoms (Chrysophytes) Green algae (Chlorophytes) Euglenoids (Euglenophytes) 1000 species Unicellular 6000 species Multicellular 1500 species Multicellular 10,000 species Unicellular 7000 species Multicellular 800 species unicellular

Brown Algae (Phylum Phaeophyta) Brown algae are the largest in size key components of marine and tidal environments due to abundance Some species such as kelp can grow to 60m Do not have true leaves or roots Specialized tissues 1. holdfast- a structure that anchors the algae to a rock or a shell 2. stipe extends from the holdfast. 3. flat leaf-like blades used for photosynthesis 4. kelp have air bladders

Red Algae ( Phylum Rodophyta) Red algae can grow to 1 m in height Have green chlorophyll to allow photosynthesis Have another pigment called phycoerythrin which is sensitive to light waves that reach deeper into the ocean. This pigment reflect red wavelengths fo light giving the algae its red colouring. They can live at depths of up to 100m Common a food and food processing Iel nori the seaweed is used to wrap sushi Carrageenan is a gel-like substance used to help ingredients mix together Often added to dairy products like ice cream

Green Algae (Phylum Chlorophyta) most are aquatic most in freshwater but can be found in saltwater also found living in sea ice, attached to trees, and in the fur of sloths Very diverse- unicellular to multicellular Most plant-like of the algae Same chlorophyll and colour as land plants Cell walls contain cellulose Store food as starch

The Shift to Land Theory that green algae the closest evolutionary relatives of land plants is based on the following evidence: Chlorophyll a and b in cells Cellulose in cell walls Store food energy in the form of starch (Bacteria, fungi, and animals store their energy as glycogen). DNA analysis shows similar sequences Adaptations to Land Need to protect from drying out System to transport water and dissolved substances System to support the body Earliest land plants were small, grew in moist places and transferred water and substances from cell to cell by osmosis and diffusion.

Despite similarities with algae, plants have some important distinctions. 1. Environment -a transition from aquatic to terrestrial habitats 460 million years ago. 2. Embryos- plants reproduce using embryos 3. Vascular tissue –used to transport materials 4. Seeds – to protect the embryo 5. Flowers

Plant Evolution

The first land plants were small and simple in structure. Vascular plants developed next. Vascular tissue transports water, nutrients and sugars throughout plant provides physical support for plant body as well Xylem – as xylem cells grow, they form long, straw-like tubes – when the cells die, their thick cell walls remain behind, forming long fibrous pipes for water to flow through – dead xylem cells are fortified with lignin, a hard substance, which makes them strong, giving the plant support and allowing the development of trees. Phloem – phloem tissue is made of vertically stacked tubes. – their walls are porous allowing materials to be exchanged between phloem and neighbouring cells. – It is responsible for the transport of sugars throughout the plant.

Vascular tissue allowed for the evolution of roots, providing a means of anchoring the plant and absorbing and transporting water and minerals. Leaves also evolved after plants develop vascular tissue. Leaves increased the surface area of the plant above ground and allowed for a better exchange of gases in photosynthesis.

Alternation of Generations (Sporic reproduction) There are two multicellular stages in the life cycle. The gametophyte (haploid cell) contain only one set of chromosomes. The sporophyte ( diploid) created when the gametes fuse The sporophyte produces spores by meiosis which develops into the haploid gametophytes.

Success Criteria I have discussed the link between plant-like protists and the plant kingdom. I am able to state how algae are classified I am able to list the differentiate between plants and algae. I am able to list the evolutionary changes that allowed the transfer to land.

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