bio flashcards

Phylogeny

-describes the evolutionary history of relationships among organisms.
-used to classify organisms into evolutionarily related groups.
-provide evidence of evolutionary history.
-Molecular data such as amino acids, DNA, or RNA sequences
-phylogenetic tree of life shows evolutionary relationships among different groups of organisms.
-reflects the speciation process.

sister groups

-Two groups that are each other's closest relatives are called

monophyletic groups

-also called clades or lineages
-reflect evolutionary relationships
-include all the descendants (living and extinct) of a common ancestor.
-they show the evolutionary path a given group has taken since its origin.

Synapomorphies

-derived traits shared between groups of organisms.
-help to define sister taxa as well as unite members of the same clade.

Principle of Parsimony

-trees with the fewest number of evolutionary changes are preferred to ones that require more because they are the simplest explanation of the data.
-Unless additional data is uncovered to support the alternate phylogeny.

ancestral trait

-aka basal trait
-characteristic that was present in the ancestor. These kinds of traits are called plesiomorphies.

derived trait

-characteristic that is different from the ancestral trait. These kinds of traits are called apomorphies.
-didn't appear in common ancestor

Eukaryotes characteristics

•Most are larger than Bacteria and Archaea, have membranous organelles, and a cytoskeleton
•DNA is in a nucleus that is surrounded by a membrane (this is a synapomorphy for Eukaryotes)
•Only eukaryotes can be multicellular

Properties of simple multicellular organisms

1. Adjacent cells to stick together via adhesion molecules.
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 multicellular organisms

1. Cell-cell communication and transfer of materials
2. Differentiation and specialization of cells
3. 3-dimensional structures resulting in some cells that are not in direct contact with the environment.

Two mechanisms transport materials in multicellular organisms

-diffusion
-bulk transport

Diffusion (and osmosis)

-the random motion of molecules, with net movement from areas of higher to lower concentration.
-effective only over small distances.
-it limits the size and shape of organisms and cells that rely diffusion to get materials from the environment.
-Some organisms remain very small. Others have flat or highly folded shapes so that most of their cells are in close contact with the environment.
-Other organisms have the cells that require resources in thin layers near their exterior, but have large interior volumes made up of inactive molecules or tissues.

Bulk transport

-any means by which molecules move through organisms at rates faster than diffusion.
-good for large complex organisms
-enabled the movement of molecules faster and across larger distances than was possible by diffusion.
-only used to move water, sugar and nutrients over long distances.

Complex multicellularity evolved at least six separate times

-in different eukaryotic groups
•Animals
•Green algae that are ancestors of land plants
•Red algae
•Brown algae
•Fungi (2 times)

Protists

-Can be single-celled, have simple multicellularity, or complex multicellularity.
-cannot be classified as an animal, plant, or fungus
-All live in some kind of watery environment (e.g. wet soil, aquatic habitats, or inside of other organisms.)

What group gave rise to land plants?

Green Algae

What distinguishes allland plants from the green algae?

•The evolution of a water-proof cuticle, and pores or stomata to allow gas exchange.
• Fertilized egg develops into a multicellular embryo while still attached to parent and is protected and nourished by parent tissue.

Land Plants Benefits

-more space
-sunlight
-carbon dioxide for photosynthesis.

Four major transformations in life cycle and structure characterize the evolutionary history of plants:

1. The evolution of alternation of generations
2. The evolution of vascular plants
3. The evolution of pollen and seeds
4. The evolution of the flowers and fruits.

Major transformation \#1 -Alternation of Generations

Every plant species alternates between two multicellular forms:
1. A haploid gametophyte generation that makes gametes
2. A diploid sporophyte generation that makes spores

What is alternation of generations?

-The change in generation between haploid and diploid form
-shift between forms that increase variability and are specialized for fertilization, and forms that increase production and are specialized for dispersal.

Challenges to living on land

-structural support
-water and nutrient acquisition
-desiccating atmosphere
-gas exchange
-mobility
-gamete dispersal
-plants must obtain water and soil nutrients below ground and get light and CO2 above ground

Bryophytes

-A moss, liverwort, or hornwort. is a nonvascular plant that inhabits the land but lacks many of the terrestrial adaptations of vascular plants.
-rely solely 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. they can grow on wet surface but dry out easily

How Bryophytes survive on land?

-desiccation tolerance
-They can survive extreme dehydration during dry conditions and recover when conditions are suitable.

Major transformation 2 - The evolution of vascular tissue.

-Vascular plants evolved roots and vascular tissue as a strategy to avoid desiccation.
-evolved roots to pull water and nutrients from soil far below ground. This means that they do not need to grow on wet surfaces.
-have a thick cuticle to prevent from drying out easily

What forms the plants bulk transport system?

-Vascular tissue forms the bulk transport system
-critical for plants to move water from non-photosynthetic parts (roots) to photosynthetic parts (stems and leaves.)
-vascular plants avoid desiccation and can continue to be active and photosynthesizing even in dry conditions.

What are vascular tissue made of?

-xylem and phloem
-xylem tissue provides rigid support for growing upright on land

Bulk Flow Mechanisms in plants

-Cohesion-Tension-Transpiration in xylem moves water and minerals from tissues with access to water (roots) to tissues without access to water (shoot systems above ground).
-Translocation in phloem moves sugars from photosynthetic tissues with access to sunlight (leaves and/or stems) to non-photosynthetic tissues (roots, buds, and reproductive structures).

Major transformation \#3

-The evolution of pollen and seeds led plants to greater independence from surface water
-Before pollen evolved, plants needed surface water for fertilization to occur. Sperm developed on male gametophytes and needed to swim to the egg over a very short distance.

Pollen grains

-tiny male gametophytes that are covered with a tough waterproof layer. These produce sperm.
-are carried by wind or animals to the location of the egg (in female gametophytes). Once there, they produce sperm and a pollen tube to transfer the sperm to the egg.

seeds

-Before seeds evolved, plants needed surface water to prevent plant embryos from drying out before they could complete development.
-A seed consists of the (sporophyte) embryo and a store of nutritive tissue, surrounded by a tough protective layer.
-allow plant embryos to survive outside of the parent plant for extended periods of time

Major transformation \#4

-The evolution of the flowers and fruits.
-Before flowers and fruits evolved, pollen was only dispersed by wind, and developing seeds were exposed to the environment.
-Flowers protect the female gametophyte, collect or disperse pollen and attract pollinators.

The evolution of fruits

help to disperse the embryonic sporophytes in the seeds away from their parents.

Differences in plant reproduction and presence or absence of vascular tissue group land plants into three functional groups:

• Nonvascular plants (Bryophytes and others)
• Seedless (spore dispersing) vascular plants
• Seed plants.

Seed Plants

- a monophyletic group that consists of the gymnosperms and the angiosperms.
-defined by the production of seeds and pollen grain

Seed plants produce two different kinds of spores

-two different kinds of gametophytes -male and female.
-occurs in different parts of the sporophyte.

Gymnosperms

-A plant that produces seeds that are exposed or partially exposed rather than seeds enclosed in fruits
-Non-flowering seed plants
-develop in either dry of fleshy cones

Angiosperms

-A flowering plant which forms seeds inside a protective chamber called an ovary.
-seed plants that produce flowers and fruits.
-The ovaries later grow to become fruits that enclose seeds.

Roots, stems and leaves are organized in two systems

-the shoot system (stems and leaves - above ground)
-the root system (below ground).

Shoot systems

-stems and leaves
-photosynthesize sugars
-conserve water
-provide aerial support at different levels

Root Systems

•anchor the plant in the soil
•absorb water and minerals
•store material produced in the shoot for later use

What do plants use to absorb materials and move them over short distances?

-use diffusion, osmosis, and active transport, to absorb materials and move them over short distances. O2 and CO2 move only by diffusion and so can move only short distances.
-work to move water, minerals, and sugar into an out of cells

Diffusion

-Molecules move from areas of higher concentrations of that molecule to areas of lower concentrations of that molecule -down a concentration gradient.
-This occurs automatically until equilibrium is reached (both sides have the same concentration) or unless it is counteracted by an opposing force.

Osmosis

-diffusion of water across a semi-permeable membrane (a membrane that prevents movement of non-water molecules)
-The movement of water depends on the concentrations of the non-water molecules - called solutes.
-Water molecules move from solutions with fewer solutes (more watery solutions) to solutions with more solutes (less watery solutions). Like diffusion, this occurs automatically unless it is counteracted by an opposing force.

Active transport

-Energy-requiring process that moves material across a cell membrane against a concentration difference
-(from areas of lower concentrations to areas of higher concentrations) requires energy from living cells.

osmotic pressure or solute potential.

-The osmotic pull on water across a membrane by hypertonic solutions
-The more hypertonic a solution is, the greater pull on water it will have.

Pure water has no osmotic pull
True or False?

-TRUE
-it is always hypotonic to other solutions

Cells are made up of pure water
True or False?

-FALSE
-always contain some solutes (they are not made of pure water!) Their osmotic pull depends on their solute concentration compared to the solution outside their membrane.

turgor pressure

-the pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell
-Cell turgor pressure helps to keep plants upright. A plant wilts when the turgor pressure of its cells is low.

Water always moves by osmosis into and out of cells.
True or False?

-TRUE, HOWEVER
-most organisms can manipulate the solute concentration of their cells to cause water to move in or out of them.
-This often requires active transport (energy generated by the cell) to increase the solute concentration in cells so that the osmotic pulling force is strong enough for water to move in by osmosis.