Origins of Multicellular Organisms

Abiogenesis

Life originated on earth from nonliving matter through natural processes.

Why is abiogenesis difficult for scientists to test

It is difficult for scientists to tests because first protocells did not form many fossils and conditions on earth have changed.

Prebiotic Earth Conditions

Water(oceans), high UV radiation, high temperatures, reducing atmospheric gases(many reactive inorganic molecules), lightning storms no free oxygen

Theory of abiogenesis

Catalysis, Self Assembly, Self Replication, Compartmentalisation

Catalysis

inorganic molecules synthesized organic molecules

Self Assembly

organic molecules assemble into polymers

Self Replication

polymers begin to self replicate(enabling inheritance)

Compartmentalisation

self replicating polymers became surrounded by membranes(creates unique internal chemistry)

Spontaneous formation of membranes

amphipathic phospholipids spontaneously form spherical micelles. It allows the internal chemistry different from exterior.

Miller Urey experiment

recreated conditions of prebiotic Earth to test non-living synthesis of organic materials

Steps of Miller Urey experiment

heat, water vapor, reducing atmosphere gases, electricity(lightning), left for week to cool, contained traces of simple organic molecules

Describe reasons why water is an essential requirement for the formation of life

polarity causes lipids to form lipid bilayers(plasma membrane), dissolves polar substances (metabolism). Its thermal properties allows for a stable environment (homeostasis)

Describe the arrival of liquid water on earth

Its first form was water vapor(the hot temperature prevented condensation). Water vapor was lost into space and cooled. Asteroids made of rock and ice formed and hit early earth. The ice melted into liquid water.

Describe the goldilocks zone

Earth is in a "Goldilocks zone" because the distance from a star creates a perfect temperature for liquid water(depends on the size and temperature of the star). Very few planets have suitable mass and atmosphere for liquid water.

Protocells

Precursors to our prokaryotes. RNA was first genetic material.

Describe the two qualities of RNA that support it being the first genetic material

Self replication forms new RNA. It was a catalyst and could create proteins

State modern day replacements of RNA for its genetic and catalytic form

DNA stores genetic material as it is more stable (double helix). Proteins are the catalysts now because of more variation with 20 amino acids in for proteins while there were only 4 RNA bases.RNA is transitional form between DNA and protein (Transcription and translation).

State what LUCA means

last universal common ancestor. All organisms on Earth share common descent from LUCA.Does not represent the first cellular organism. Probable other lifeforms coexisted with LUCA( shared genes).

Describe LUCAs connection to the three domains of life

Immediate ancestor of three domains of life: bacteria, archaea, and eukaryotes

Outline evidence for the common ancestry of living organisms

All cells have same 4 nucleotides in their DNA(ATCG). All cells have same 64 codons to make their amino acids. Sequence of bases and amino acids make organisms different.

Outline the LUCA evidence

~2 to 4 billion years ago. Seafloor Hydrothermal vents contain fossils of prokaryotes(~3.7 billion years old). minerals precipitate out hydrogen for energy. Gene for high temperature environments

Describe the endosymbiotic theory

Large prokaryotes used endocytosis to engulf small aerobic bacteria and eventually created eukaryotic cells.

Endosymbiont

cell living inside another cell with mutual benefits

Outline evidence for the endosymbiotic theory

Mitochondria and chloroplasts have naked and circular DNA, 70s ribosomes are the same size as bacteria, and have membrane proteins similar to prokaryotes

Size comparisons

molecule : 1 nm, membrane thickness : 10 nm (on organelles), virus : 100 nm, bacteria : 1 um, organelles : up to 10 um, Most eukaryotes : up to 100 um

Describe the surface area / volume and cell size relationship

Cells only grow to a volume with enough surface area to exchange materials needed for metabolism. The larger the cell, the more materials needed for metabolism. Typical cell growth causes volume to increase faster than surface area

multicellular organisms

Multicellular organisms are multiple eukaryotic cells operating in unison.

Advantages of multicellular organisms

Exceed size limits of SA:Vol ratio, high complexity (Differentiation and emergent properties), and longer lifespans

Disadvantages of multicellular organisms

cancer

Describe the variation of cell size in multicellular organisms

Cell size in multicellular organisms varies. Sizes are for optimal function.

Size of red blood cells and purpose

Red blood cells are small (7

Size of neurons and purpose

Neurons(very long but not wide) transmit signals throughout body

Size of striated muscle fibers and purpose

fused muscle cells for more width and length

Size of ovum(egg) and purpose

ovum(egg) very large (120um)

Size of sperm and purpose

Sperm very small(~5 um)

List traits of cells that exchange materials in multicellular organisms

Cells that exchange materials have large surface area and long and flat shape. Tissues can have villi and microvilli (finger like projections).

describe emergent properties

Multicellular organisms have emergent properties. Characteristics and functions that appear as cells begin to work together. Higher levels couldn't appear without the preceding levels.

Examples of emergent properties

Levels of anatomical organization: Cell, tissue, organ, organ system, organism

Describe how differentiation leads to specialized tissues

Multicellular organisms can develop specialized tissues from stem cells. All cells of an organism contain the same DNA/genome. Certain genes are turned on and off to make them specialized/differentiate by making specific proteins. chemical signals cause this

describe differentiation

stem cells become more specialized and distinct from one another as they mature

State characteristics of stem cells

Self renewal, Potency. Stem cells in animals are created at fertilization with the creation of the zygote.

Potency

can differentiate into specialized cell types necessary for multicellular organism development

Self renewal

continuously divide and replicate

Totipotent

forms any cell type, Develop into new organisms, Embryonic

Pluripotent

forms any cell type arising from three germ layers, embryonic

Multipotent

Some closely related cell types, adult

Describe a stem cell niche

Area where adult stem cells are maintained

Outline 2 examples of adult stem cells and their therapeutic purposes

Bone marrow, Hair follicles

Bone marrow stem cell niche

Hematopoietic stem cells create blood cells. Used as leukemia treatment

Hair follicles stem cell niche

Epidermal stem cells used for hair, skin, vascular, wound repair and burn and baldness treatment

Discuss the use of stem cells for therapeutic purposes

Stem cells replaced damaged or diseased cells

Ebryonic stem cell advantages and disadvantages

Great potency ethical issues

Adult stem cells advantages and disadvantages

Lower potency, less ethical issues. lower chance of rejection

State the name of undifferentiated tissue in plants

Meristematic tissue

Meristematic tissue

Not technically stem cells (animals). Found in tips of roots and shoots

State the 3 main types of stem cells

Totipotent, Multipotent, Pluripotent