L14 - Diversity of Life

What are the 3 ways to track biology (and evolution)?

1. Stromatolites (layered, rocky structures formed by microbial mats (cyanobacteria))

2. Isotope ratios (biological processes prefer lighter isotopes (i.e. carbon-12 over carbon-13)

3. Microfossils (looking at fossils and finding cells for evidence of early organisms)

What did the Miller-Urey 1953 test for?

Tested whether chemical evolution could happen on early earth & Proved life’s basic building blocks can form naturally from non-living chemicals

Describe/Explain how the Apparatus in the Miller-Urey experiment worked

• The ocean flask: heated water boiled to create water vapor, representing the warm ocean

• The atmosphere chamber: water vapor mixed with gases and that represented gases in early Earth (methane, ammonia, hydrogen, and water)

• The spark (lightning): electric sparks in the mixture represented the lightning storms

• The condenser: cooling tube that turned vapor back into liquid, which followed down into a trap, representing the water vapor

What did the Miller-Urey experiment reveal?

the formation of the macromolecules

1. carbohydrates

2. proteins

3. nucleic acids

4. lipids

Define what protocells are and what they are made of and the 3 things they can do.

self organizing pre-cell structure that represents a potential step in the origin of life (made of bubble fatty acids and traps important molecules like RNA inside)

1. reproduce themselves (self-replicating)

2. are variable (can look different for each one as mutations can occur)

3. have fitness differences

Identify the difference between Prokaryotic v. Eukaryotic Cells (in terms of nucleus, membrane-bound organelles, size, DNA structure, and internal compartmentalization)

Prokaryotic cells:

• no nucleus

• absent membrane-bound organelles

• small size

• DNA structure is circular, a single chromosome

• internal compartmentalization is minimal/none

Eukaryotic Cells:

• true nucleus enclosed by a nuclear membrane

• membrane-bound organelles like mitochondria, ER, Golgi apparatus

• large size

• DNA structure, linear multiple chromosomes

• internal compartmentalization is extensive with internal membranes

Endosymbiotic Theory

where one organism lives inside the other

Primary endosymbiosis

when a host cell (an early eukaryote/archaeon) ingests a free-living prokaryote (a bacterium). This is when the mitochondria and chloroplasts are originally formed (mitochondria first, then chloroplasts)

Describe the process of formation of mitochondria

1. Anaerobic prokaryotes (cells that couldn’t use oxygen) ingest aerobic prokaryotes (cells that could use oxygen to make energy) for food to produce for energy 

2. Normally, the predator cell would release digestive chemicals into the membrane bubble to break down the food. However, the prey cell (aerobic prokaryotes) survived into the cytoplasm) 

3. A symbiosis (mutual) relationship formed → endosymbionts: the small aerobic cell received shelter and in return, the anaerobic cell received oxygen. Over millions of years, the small anaerobic cell evolved into a mitochondria

4. Cells that only went through this process became animals and fungi (they have mitochondria, but no chloroplasts)

Endosymbionts

any organism that lives inside the body or cells of another organism (aerobic prokaryotes living in the cytoplasm) and forming a mutualistic relationship

What can the endosymbiotic theory be supported by?

the presence of circular mtDNA (mitochondrial DNA), which is similar to the circular DNA found in prokaryotic cells (which proves that it was a prokaryote being developed into a mitochondria)

Describe the process of formation of chloroplasts

1. The cell swallowed a different type of prokaryote: cyanobacterium that could use sunlight to make sugar

2. Like before, the cell stayed alive inside the cytoplasm and a new mutual relationship formed. The host cell provided shelter and raw materials (like carbon dioxide) and in return, the photosynthetic prokaryote used sunlight to produce food (sugar) for the host

3. This evolved into the chloroplast

4. Cells that went through Step 1 AND Step 2 became plants and algae (they have both mitochondria and chloroplasts)

Define the process of the secondary endosymbiosis

one large eukaryotic cell swallowing another eukaryotic cell (the primary alga) that already has a chloroplasts, and that cell gets organelles from two lineages (from the original cell and then the cell that had the mitochondria/chloroplasts)

Endocytosis

the way a cell “swallows” things from outside to bring them inside; a cell swallows materials from its external environment using its plasma membrane to bring them inside

Describe the process of the formation of the nucleus, ER, and the Golgi Apparatus

Nucleus: some of the membrane folds wrapped completely around the cell’s DNA and fused together, trapping DNA inside its own bubble, creating the nuclear envelope

Endoplasmic Reticulum (ER) and Golgi Apparatus: remaining leftover pieces of folded in membranes floated off into the cytoplasm and shaped themselves into other factories of the cell 

Name at least 5 adaptations plants gained in evolving from water to land.

• Cuticle: waxy layer to reduce water loss

• Stomata: pores that open up and close to regulate gas exchange and water balance 

• Support structures: rigid cell walls for upright growth

• Rhizoids/roots: anchoring and nutrient uptake from soil

• Protected gametes/embryos: gametangia and embryo retention within the parent plant (“womb-life” system) → early step toward seeds

• Spores with sporopollenin: durable coating for survival on land

Gametophyte

“gamete-plant”; body phase of the plant that makes gametes (sperms and eggs)

Sporophyte

“spore-plant”; body phase of the plant that makes spores (tiny, tough survival pods)

Spores

tiny, single-celled biological seeds. It lands on the ground and grows into a brand-new plant body all by itself

Describe the whole process of Gametophyte and Sporophyte cycle

1. The Gametophyte (n) makes sperms and eggs

2. The sperm and egg meet (fertilization) to create a baby cell with two sets of DNA (2n)

3. The baby cell grows into the Sporophyte (2n) 

4. The Sporophyte makes spores (n), which floats away, land in the dirt, and grows into a Gametophyte

What is the evolutionary trend of Gametophyte and Sporophyte?

when plants lived in water (aquatic algae), they didn’t have to worry about the harsh sun frying their DNA, and they didn't have to stand upright. Because of this, the Gametophyte (one set of DNA) was a big, visible boss. But as plants evolved to conquer dry land, the gametophyte shrank → the Sporophyte became dominant

Why did plants evolve to favor the diploid (sporophyte) generation?

To increase variation, needed to improve the generations that were now living on land (since they had the advantageous traits of vascular tissue, stomata, etc)

Mosses, Ferns, and Trees/Flowers → Label whether or not if they are Gametophyte-dominant or Sporophyte-dominant

1. Mosses (The Beginning - Barely out of the water)

• Gametophyte-dominant 

2. Ferns (The Intermediate Level - Moving inland)

• Sporophyte-dominant

3. Trees and Flowers (The Masters of Land - Gymnosperms & Angiosperms)

• Sporophyte-dominant (while having a mix of the two)

Describe the Evolutionary trend in Animals

Origin of Multicellularity: single-celled to multicellular organisms with specialized cells (division of labor among cells, early animals evolved form colonial protists; a group of single-celled eukaryotic organisms of the same species, living in a group for mutual benefit)

Origins of Tissues: no tissues → tissues → organized body parts

• Sponges (porifera): no true tissues

• Cnidarians (jellyfish, corals): two tissue layers (diploblastic): ectoderm and endoderm 

• Bilaterians: three tissue layers (triploblastic) → ectoderm, mesoderm, endoderm

Origins of Gas Exchange in Water → specialized respiratory surfaces; evolving of gills (in fish)

Describe the evolution of reproduction and development (what was the trend)? Name the example of this evolution/reproduction and describe its evolved traits.

• Trend: external fertilization → internal fertilization; simple development into complex life cycles

• Example of this evolution of reproduction: Tiktaalik Roseae 

  • Evolved fish traits: fins with fin rays, gills and scales, tail adapted for swimming, spiracles (openings) on top of the head used for air breathing

  • Evolved tetrapod traits: flat head with upward facing eyes useful in shallow water and for looking above surface

Name the chordates traits and what each part is

Notochord – flexible rod providing support

Dorsal hollow nerve cord – develops into brain and spinal cord

Pharyngeal slits/pouches – function in filter feeding or respiration (become jaws/ears in vertebrates)

Post-anal tail – aids in locomotion or balance

Endostyle/thyroid gland – involved in metabolism and filter feeding

Name the shared traits between humans and primates

1. Forward facing eyes (stereoscopic vision)

2. Grasping hands and feet with opposable thumbs

3. Nails instead of claws

4. Large brains relative to body size

5. Extended parental care and complex social behavior

Name the individual human traits that make them unique

1. bipedalism: free hands for tools, changes pelvis, spine & skull orientation

2. larger brain (esp. neocortex): language, abstract thought, culture

3. reduced jaw and teeth: diet change, tool use

4. complex communication: spoken language and symbolic thought

5. culture and technology: transmission of learned behaviors across generations

How does context change gene expression?

humans share ~98-99% of DNA with chimpanzees but differences lie in gene regulation/expression (not entirely new genes)

Genes for brain development (FOXP2 or HAR1) influence language and brain growth

Genes for jaw muscle and skull development (MYH16) influence brain size and facial shape

Sponges (porifera)

no true tissues

Cnidarians (jellyfish, corals)

two tissue layers (diploblastic): ectoderm and endoderm

Bilaterians

three tissue layers (triploblastic) → ectoderm, mesoderm, endoderm