Protista were the first eukaryotes and ancestors to

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Protista were the first eukaryotes and ancestors to other eukaryotes Land plants evolved from

Protista were the first eukaryotes and ancestors to other eukaryotes Land plants evolved from Protista Color branches= Protista 1 Animals evolved 1 From Protista

Evolution of Land Plants 2 2

Evolution of Land Plants 2 2

Evolution of Land Plants ~500 million years ago • First multicellular organism that could

Evolution of Land Plants ~500 million years ago • First multicellular organism that could survive completely exposed to air • Only life on land prior to plants-prokaryotes and single-celled Protists • Allowed for aquatic animals to survive on land 3

Why did it take ~ 4 billion years for plants to appear on land?

Why did it take ~ 4 billion years for plants to appear on land? What had to be present in atmosphere for these larger multicellular organisms to survive on land protected from sun’s radiation? OZONE 4

Protists to Land Plants It all started with Green Algae • Aquatic plant-like member

Protists to Land Plants It all started with Green Algae • Aquatic plant-like member of Protista • Closest relative to land plants • Similarities between green algae and land plants suggest land plants evolved from green algae 5

Protists to Land Plants and Green Algae form a monophyletic group which means …

Protists to Land Plants and Green Algae form a monophyletic group which means … … homologous characteristics shared among green algae, land plants and their common ancestor 6 6

ex. ferns ex. moss ex. Pine trees Flowering plants The earliest land plants evolved

ex. ferns ex. moss ex. Pine trees Flowering plants The earliest land plants evolved from green algae and are very similar to them. These early land plants then diversified. as you move up the tree, the plants look less and less like 7 green algae 7

ex. ferns ex. moss ex. Pine trees Flowering plants The moss pattern shown on

ex. ferns ex. moss ex. Pine trees Flowering plants The moss pattern shown on this tree is a “star phylogeny” and suggest that several types of mosses evolved relatively close in time, so close in fact researchers aren’t sure which lineage came first. Write an explanation regarding why such a rapid diversification would happen 8 8

Remember: What is a synapomorphy? 1. Shared derived trait that is present in 2

Remember: What is a synapomorphy? 1. Shared derived trait that is present in 2 or more taxa most recent common ancestor but is missing in distant ancestors 2. Evolutionary unit that includes an ancestral pop an all its descendants but w no other 3. Evolutionary unit that includes an ancestral pop but not ALL of its descendants 9

Synapomorphies • chlorophyll a and chlorophyll b • carotenoids as accessory photosynthetic pigments •

Synapomorphies • chlorophyll a and chlorophyll b • carotenoids as accessory photosynthetic pigments • double-membrane chloroplasts containing stacks of thylakoids (grana) • energy stored as starch inside the chloroplast in which it is produced • cell walls composed of cellulose and pectin cell wall construction via cell plate formation at the end of mitosis 10

32 Plant cell structure You don’t need to know all the parts, but you

32 Plant cell structure You don’t need to know all the parts, but you should have an idea of what is in the cell. endoplasmic reticulum nucleus central vacuole Golgi Cell membrane chloroplasts cell wall mitochondria 11 11

Cells walls of Plants and Green Algae Composed of Cellulose • Polysaccharide of glucose

Cells walls of Plants and Green Algae Composed of Cellulose • Polysaccharide of glucose monomers • Provides a structural frame-work • Cellulose is the most rigid material for a cell wall- provides most support 12 Cellulose (color enhanced imaging) Focus on the organization, not the specifics

For Comparison: Other Protists Have Different Cell Walls Some Protista (like one that causes

For Comparison: Other Protists Have Different Cell Walls Some Protista (like one that causes SDT, Tricomoniasis): No Cell Wall Diatoms: Cell Wall made of silica (glass-like cell walls) Trichomonas Vaginalis diatoms Other Protists have Cellulose in combination with other 13 materials

Chlorophyll b 14 • All photosynthetic organisms have chlor a (evolved first, in bacteria)

Chlorophyll b 14 • All photosynthetic organisms have chlor a (evolved first, in bacteria) • Chlor a best at absorbing light through water • Chlor b evolved in green algae to absorb light better in shallow water and on land. • Green algae & land plants have a &b Figs 10. 6 and 10. 814

Green Algae and Plants (but not other Photosynthetic Protists) make Starch as a Storage

Green Algae and Plants (but not other Photosynthetic Protists) make Starch as a Storage Molecule 3 CO 2 rubisco 6 ATP Calvin Cycle 3 ADP 6 NADPH 3 ATP 6 NADP+ cytosol Glucose Sucrose Disaccharide (glucose + fructose) transported to diff parts of plant and immed. used for Cell Respiration in chloroplast Starch polysaccharide of glucose monomers 15 used at night when no photosynthesis

Algae at surface of water and coastal edges would experience alternating wet and dry

Algae at surface of water and coastal edges would experience alternating wet and dry conditions Those with adaptations that allow them to survive in longer periods of desiccation would be more likely to survive How might the characteristics first seen in green algae and also in land plants provide an advantage in drier conditions?

Survival on land • Natural selection favored individuals with the following characteristics – Chlorophyll

Survival on land • Natural selection favored individuals with the following characteristics – Chlorophyll b: absorb λ of light passing through shallow water or no water better than chlorophyll a – Cellulose: more rigid, so more structural support for remaining upright when can’t float on water – Starch: Allows plants to use stored sugar at night for cell respiration when no photosynthesis…

Interesting… • why starch/storage wasn’t/isn’t necessary for aquatic phototrophs (i. e. diatoms, single-celled green

Interesting… • why starch/storage wasn’t/isn’t necessary for aquatic phototrophs (i. e. diatoms, single-celled green algae), we don’t understand.

Land plants evolved from green algae which is surrounded by water How did plants

Land plants evolved from green algae which is surrounded by water How did plants adapt to living on dry land? ? What are some of the struggles with being on dry land? Dessication (Drying out) Standing upright Getting water from soil to rest of plant 19

Dealing with Dry Land Problem: Plants can’t move to the water to avoid water

Dealing with Dry Land Problem: Plants can’t move to the water to avoid water stress Solution: • Prevent water loss from cells (evaporation) • Transport water from tissues with direct access to water to tissues without access (not all plants need to do this, only taller ones) Adaptation for this solution: Develop specializations (specialized cells) to prevent evaporation of water and to transport water 20

Land Plants - Adaptations to Terrestrial Living ts e red a alg gre en

Land Plants - Adaptations to Terrestrial Living ts e red a alg gre en ae g l a no asc v n r ula n pla s s dle see sc va ts n la p sp gy o mn s s erm io g an Cuticle Pores & Stomata See Fig. 29. 9 21 rm e p s 21

Cuticle Epidermis = single layer of cells covering entire plant body Cuticle = layer

Cuticle Epidermis = single layer of cells covering entire plant body Cuticle = layer of wax/fat (nonliving) covering epidermis and secreted by epidermis Works as a sealant covering the above-ground part of plants and dramatically reduces water loss to surrounding air Cuticle on stem of plant 22 22

“If biologists had to point to one Innovation that made the transition to land

“If biologists had to point to one Innovation that made the transition to land possible, it would be the … cuticle. ” -Freeman textbook

Cuticle thickness varies with climate… To reduce water loss in hot and/or dry areas,

Cuticle thickness varies with climate… To reduce water loss in hot and/or dry areas, thickened cuticle Fig. 30. 10 24

Recall equation for photosynthesis… Light + H 2 O + CO 2 + sugar

Recall equation for photosynthesis… Light + H 2 O + CO 2 + sugar CO 2 gas must enter plant through leaves/stem from atmosphere, but cuticle is impervious to CO 2 from atmosphere Fig. 30. 10 Stoma: opening (pore) surrounding by guard cells (pl; stomata) 25 25

Guard cells can change shape to close stomata guard cells Like 26 Fig 10.

Guard cells can change shape to close stomata guard cells Like 26 Fig 10. 21 pore Stoma (sng. ) Stomata (plu. ) guard cells full of water ->taught ->somata ->CO 2 in (when OK to risk water loss) (when conditions are dry…? )

Should stomata be open day and/or night? 27

Should stomata be open day and/or night? 27

DAY: • CO 2 used in Calvin cycle which doesn’t require light but need

DAY: • CO 2 used in Calvin cycle which doesn’t require light but need energy (ATP…) from light reactions which do. • Can ATP from light reactions be stored for use at night? • NO, so Calvin Cycle only during day so • must open stomata to let CO 2 in during the day, despite water loss. 28

Desert? • Alternative store CO 2 • Alternative would be to collect CO 2

Desert? • Alternative store CO 2 • Alternative would be to collect CO 2 during the night and store it for use during the day but hard to store. • Some specialized desert plants do open stomata only at night to avoid water loss but NOT the norm. 29

Adaptations that slow water loss: • Stomata • cuticle 30

Adaptations that slow water loss: • Stomata • cuticle 30

Next Challenge: Physical Support Algae could float Ability to develop and withstand water pressure

Next Challenge: Physical Support Algae could float Ability to develop and withstand water pressure in cells to keep them “inflated” Even low-growing plants like mosses and ferns need support for leaves to remain up-right (which allows more of leaf’s surface area to be exposed to sunlight) 31 31

Land Plants - Adaptations to Terrestrial Living ts e red a alg See Fig.

Land Plants - Adaptations to Terrestrial Living ts e red a alg See Fig. 29. 9 32 gre en ae g l a no asc v n r ula n pla s see s dle sc va ts n la p sp gy o mn s s erm rm e p s io g an Cuticle Pores & Stomata Generate high turgor 32 pressure

Recall Osmosis If cell is placed in surrounding solution with lower solute concentration than

Recall Osmosis If cell is placed in surrounding solution with lower solute concentration than inside cell (assume solute can’t cross mem. ) then water rushes into the cell… cell may burst!! The solution is HYPOTONIC relative to the cell part Fig 6. 16 33 What would keep the cells from bursting?

Plant Response to water by osmosis Hypotonic Environment Animal Cell Plant Cell 34 Isotonic

Plant Response to water by osmosis Hypotonic Environment Animal Cell Plant Cell 34 Isotonic Environment Hypertonic Environment

For PLANT CELLS it is ideal for the solution to be HYPOTONIC relative to

For PLANT CELLS it is ideal for the solution to be HYPOTONIC relative to the cells cell wall solutes pressure water cell membrane Water moves in by osmosis Cell walls resist swelling and pressure builds = TURGOR PRESSURE 35

Note that leaves have become limp but stem is still upright due to structural

Note that leaves have become limp but stem is still upright due to structural support from lignin (we’ll discuss soon). 36