BIO 130 - Nesmith Exam 3

what is phylogeny?

describes the evolutionary history of relationships among organisms

Phylogenetic tree of life

shows evolutionary relationships among different groups of organisms

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

Monophyletic group (Clade)

an ancestor and all of its descendants

Ancestral Trait

A trait shared by all members of a group through a common ancestor.

called plesiomorphies

Derived trait

newly evolved features that do not appear in common ancestors

called apomorphies

Synapomorphie

a derived trait shared by taxa due to common ancestry

Sister groups

two groups that are each others closest relatives

Fossil record

information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived

Phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms

Clade

A group of species that includes an ancestral species and all its descendants.

Modern Classification

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Paraphyletic

Describes grouping that include some, but not all, the descendants of a common ancestor

does not represent the phylogeny of organisms

Polyphyletic

Describes groupings that do not include the last common ancestor of all members.

does not represent the phylogeny of organisms

Eukaryote

Include everything from tiny single-celled organisms to trees and blue whales

Have membranous organelles, and a cytoskeleton

DNA is in a nucleus that is surrounded by a membrane

Only Eukaryotes can be multicellular

Prokaryote

A unicellular organism that lacks a nucleus and membrane-bound organelles

example: blue-green algae, bacteria, and mycoplasma

Simple multicellularity

1) Adjacent cells to stick together
2) Little to no communication or transfer of resources between cells
3) Little differentiation of cell types - most or all cells retain a full range of functions including reproduction
4) Every cell is in contact with the external environment

Complex Multicellularity

Very different from one another, all have:
1) Cell-cell communication and transfer of materials
2) Differentiation and specialization of cells
3) 3D structures resulting in some cells that are not in direct contact with the environment

What are the challenges of organisms becoming larger and how do they overcome it?

They have more interior cells that are not in contact with the outside environment. A challenge is transporting materials to these interior cells

Two mechanisms transport materials in multicellular organisms: Diffusion and bulk transport

Diffusion (and osmosis)

The random motion of molecules, with net movement from areas of higher to lower concentration

Bulk transport

any means by which molecules move through organisms at rates faster than diffusion

Disadvantages of Diffusion

Only effective over small distances
limits size and shape of organisms and cells that rely diffusion to get materials from the environment

Structural adaptations to facilitate diffusion in large organisms

Human circulatory system

Vascular tissues in trees

Protists

Can be single-celled, have simple multicellularity, or complex multicellularity

All live in some kind of watery environment (wet soil, aquatic habitats, or inside other organisms)

Why are protists not a monophyletic group

They are scattered around the remaining eukaryote taxa after eukaryote groups with complex multicellularity

does not contain all descendants of its most recent common ancestor).

Why did plants move to land?

More space, sunlight and carbon dioxide for photosynthesis

What challenged did plants face due to moving on land?

Obtaining resources and desiccation (dry out)

4 major transformations in land plant evolution

The evolution of alternation of generations
The evolution of vascular plants
The evolution of pollen and seeds
The evolution of the flowers and fruits

The evolution of alternation of generations (major transformation 1)

every plant species alternates between 2 multicellular forms
1. A haploid gametophyte
2. A diploid sporophyte generation that makes spores

Alternations of Generations

plants can shift between forms that increase variability and are specialized for fertilization, and forms that increase production are specialized for dispersal.

Cuticle

A waxy covering on the surface of stems and leaves that acts as an adaptation to prevent desiccation in terrestrial plants.

a waterproof layer

Bryophytes

Plants that rely soley on diffusion to absorb water. They must remain small and can absorb only surface water to keep their photosynthetic cells hydrated. Cuticle layer is thin, can grown on any wet surface, can dry out easily.

Dessiccation tolerance

bryophyte strategy

Can survive extreme dehydration during dry conditions and recover when conditions are suitable

The evolution of vascular plants (major transformation 2)

Vascular plants evolved roots and vascular tissue as a strategy to avoid desiccation

Roots pull water and nutrients from soil far below ground. Do not grow on wet surfaces. Thick cuticle to prevent dry out

bulk transport system

can move water and nutrients faster than diffusion over longer distances.

Vascular tissue, Vascular plants

Vascular tissue

made up of xylem and phloem

Cohesion-Tension-Transpiration in xylem

bulk flow mechanism

moves water and minerals from tissues with access to water (roots) to tissues without access to water (shoot systems above ground)

Translocation in phloem

bulk flow mechanism

moves sugars from photosynthetic tissues with access to sunlight (leaves and/or stems) to non-photosynthetic tissues (roots, buds, and reproductive structures)

How are gases transported in plants

Only by diffusion, not by bulk flow

Challenges of living on land

scarcity of water and lack of structural support

Vascular plants

evolved roots to pull water and nutrients from soil far below ground. This means that they do not need to grow on wet surfaces. Since their above-ground parts do not need to absorb water from surfaces, they have a thick cuticle to prevent them from drying out easily.

Xylem

vascular tissue that carries water upward from the roots to every part of a plant

provides rigid support for growing upright on land.

Phloem

Living vascular tissue that carries sugar and organic substances throughout a plant

Root Systems

Anchor the plant in soil
Absorb water and minerals
Store material produced in the shoot for later use

Shoot System

Photosynthesize sugars
conserve water
provide aerial support at different levels

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

Diffusion of water across a semi-permeable membrane

active transport

Material moving against the concentration gradient. Requires energy
water cannot move through ATP in a membrane

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes

Isotonic

when the concentration of two solutions is the same

Hypotonic

Having a lower concentration of solute than another solution

Turgor Pressure

The pressure that water molecules exert against the cell wall

Helps keeps the plant upright. When pressure is low, a plant will wilt

Osmotic pull

occurs when a solution is more concentrated on one side of a permeable membrane and less concentrated on the other side

depends on their solute concentration

Pores (stoma)

Plants have these to absorb CO2 through their cuticle.

Guard Cells

Plants have these (2 guard cells) around the stoma (pores) so they can regulate gas exchange and limit water loss

How does diffusion, osmosis and active transport work together to open and close guard cells?

The guard cells can shrink (close, low-volume state) and solutes and water leave or they can swell (open, high-volume state) where water and solutes come in, changing the size of the pore and opening or closing the stoma

Which transport mechanisms in plants are bulk transport systems?

Transport through Vascular Tissue, take place in Xylem and Phloem,

Xylem anatomy

Greatly elongated pits for water flow
Xylem cell walls contain lignin that increases strength
When the mature cells die, the leave behind thick cell walls
Cells walls form hollow connected tubes where water flows

Mature Xylem

Thick cell walls without cytoplasm or cell membranes.

How is the structure of Xylem related to its function

Water and minerals are transported in the xylem over long distances without crossing any cell membranes, meaining that water cannot move by osmosis

Xylem reiles on tension (pulling force) and moves from roots to shoots

What does long distance travel in the pholem rely on to move in different directions?

Pressure (a pushing force)

cohesion-tension theory

Water is pulled to the top of trees by evaporation of water at leave surfaces

Movement of water and minerals is upwards and movements is passive (does not require energy from the plant)

evidence of cohesion-tension theory

If xylem is under tension, then xylem cells will tend to narrow as tension is increased. (Like sucking on a straw)

How does transpiration work?

Risks of transpiration

If the rate of transpiration increases, the rate of absorption of water by the root increases too. Factors that affect the rate of transpiration also affect water uptake by the plant. If water is scarce, or the roots are damaged, a plant may wilt.

transpiration

Evaporation of water from the leaves of a plant

Why do plants need to move more water than they need for metabolic purposes?

Water must evaporate to create tension to move water and minerals
Helps cool the leaves so plant doesn't get too hot
CO2 enters plant and leaves thru open stoma

What provides energy for transpiration?

the sun

Cohesion

Water molecules stick to each other

Adhesion

Water molecule ssticking to the walls of xylem cells

Tension

The pull generated by evaporation at the leaves is transmitted through water in the xylem all the way down to the water in the xylem of roots

What causes tension in xylem cells?

The pull from evaporation

What is the pressure inside the xylem cells in a tree compared to the outside?

negative (a pulling force)

What is cavitation?

it disrupts the continuity of the water column

Occurs when the water in a xylem cell is abruptly replaced by an air bubble

How does cavitation affect transpiration?

conduits can no longer transport water from the soil when cavitation occurs

What would happen to a plant if the xylem tube was blocked?

it might result in loss of availability of water in surrounding receiver cells; which ultimately reduces the turgor pressure. This will lead to loss of rigidity of cells and lead to wilting.

Under what environmental conditions do plants lose the most water?

At higher temperatures

Photosynthesis-transpiration compromise

The balance between conserving water and maximizing photosynthesis

Translocation

the movement of materials from leaves to other tissues throughout the plant.

In what directions does the sugar move in the phloem?

The movement of sugars in phloem is upwards and downwards

How does the plant move sugar in the phloem?

Translocation

Source

a tissue where sugar enters the phloem

Sugars are high in concentration

Sink

tissue where sugar exits the phloem

Sugars are low in concentration

How is the structure of phloem related to its function?

They consist of sieve elements and companion cells

Sieve elements

tubes connected end to end
lost most of their intracellular structure, but they are alive and retain their cytoplasm and cell membranes

Companion Cells

next to each sieve element
carries out cell functions like protein synthesis
Connected to sieve by strands of cytoplasm - plasmodesmata

protein synthesis

the formation of proteins by using information contained in DNA and carried by mRNA

Phloem loading

moving sugar into phloem
Sugar movs by diffusion or ATP from source cells into phloem cells

Increases sugar levels in phloem cells make them hypertonic and increases their osmotic pull. Causes water to move into phloem from the xylem by osmosis

Phloem unloading

moving of sugar out of phloem
Sugar moves by diffusion or ATP from phloem cells into sink cells

When sugar unloaded by sink cells, phloem cells become less hypertonic and have less osmotic pull. Water gets pulled bakc into nearby xylem cells by tension.

How do phloem loading and unloading set conditions for translocation? (bulk flow)

Creates high pressure at source locations
Sap pressure pushes sugary sap through phloem
Water gets pulled out of phloem by tension as sinks (low sap pressure)

Sap pressure carries sugar within phloem over long distances by passive transport

ATP or diffusion moves sugar into and out of the phloem over a short distance (Cell to Cell)

When is ATP used to move sugars in and our of the phloem?

ATP or diffusion moves sugar into and out of the phloem over a short distance (Cell to Cell)

What is some evidence for translocation theory?

Sap flow in phloem
Pressure mesaured inside of phloem cells is positive (a pushing force)
Pressure inside of xylem cells is negative (pulling force)
These forces are different from osmosis or tugor

translocation vs transpiration

Transpiration is the evaporation of water from the leaves in the form of water vapour whereas translocation is the transportation of synthesized products (sugars)in a plant. *Transpiration always occurs against the gravity while translocation does not always occur against gravity.

Function of roots

to anchor a plant into the ground, absorb water and nutrients from soil

What is the functional significance of surface area to volume ratios?

Structures with large surfaces relative to volume have more of their cells exposed to the environment and fewer interior cells to which they must transport materials

Large volumes compared to surface area is more efficent to store materials and limits exposure to the environment

3 different ways water and minerals get from soil into xylem

To reach the xylem at the center of the root, water and minerals move from the soil through the root epidermis, cortex, and endodermis. Plants do this using diffusion, osmosis and active transport.

What role does ATP play in getting water and minerals from soil into xylem?

root epidermis cells must pump the ions from the soil into the root cells by active transport

The now hypertonic cell has a strong osmotic pull to bring water into roots.

How do water and minerals move through the root cortex?

1) The symplast route
2) The transmembrane route
3) The apoplast route

Symplast route

water and minerals move across the cell membrane of the root epidermis and move from cell to cell by interconnected cytoplasm.

The transmembrane route

water and minerals move across the cell membrane of the root epidermis and move from cell to cell across the cell membranes of the cortex cells .