TXST Dr. Vargas BIO 1321.001 - Exam 2

How was the earth formed?

a supernova happened and the shock waves condensed a cloud of dust and other particles to create a star--our sun. ---> the sun then created a gravitational pull, keeping the cloud in orbit as it condensed the cloud of dust into asteroids and then planets.

Characteristics of Early Earth

- no atmosphere

- no ozone=extremely high UV rays

- HIGH amounts of methane, ammonia, water, & hydrogen

- a lot of meteorites

- constant volcanic eruptions & electrical storms (lightning)

prebiotic simulation

- experiment to mimic early earth

- mixed gases present in early earth then added UV light, heat, or an electrical charge ('lightning')

---> in these conditions, organic molecules form in a few days

organic molecules

carbon-based molecules (building blocks of life)

Hypothesis for the Beginning of Life

simple organic molecules combined into complex molecules, which combined to make the earliest, most simple cells

Panspermia

a theory that life did not originate on Earth but arrived in the form of bacterial spores or viruses from an extraterrestrial source on meteorites

prokaryotes

- first living organisms

- primitive bacteria

- arose in oceans

- lived without oxygen

- survived on organic molecules for energy

- eventually used the abundant sunlight for energy (photosynthesis)

- 2 domains: bacteria & archaea

photosynthesis

- using light energy (sun) to create chemical energy

- sunlight=constant & abundant, so no competition

oxygen

- product of photosynthesis

- early photosynthetic lifeforms created the atmosphere by providing oxygen

aerobic metabolism

- metabolism that can proceed only in the presence of oxygen.

- could harvest more food

eukaryotes

organisms made up of one or more cells that have a nucleus and membrane-bound organelles

multicellular organisms

- organisms composed of many cells (Ex. tissue, humans, etc.)

- cells can specialize (root, stem, photosynthetic, etc.)

algae

- 1st multicellular organisms in ocean

- multicellular, autotrophic, plant-like protists

order of organism development

1. prokaryotes

2. eukaryotes

3. multicellular organisms

4. land plants

5. land animals

6. amphibians

7. reptiles

-- dinosaurs

8. birds

9. mammals

1st organism on land

plants

2nd organisms on land

animals (lobefin fish)

amphibians

vertebrates that live in water and on land, smooth skin covers body, lay eggs, cold blooded

reptiles

vertebrates that live on land, scales cover body (waterproof), lay eggs, cold blooded, improved lungs for breathing outside of water

birds

- May or may not fly, with vertebra, lay eggs, have feathers

- developed from feathered reptiles

- feathers = insulation to prevent heat loss

mammals

- Living things with vertebra, hair or fur, gives birth to babies, feed the babies milk form their bodies & warm blooded.

- developed hair for insulation

- earliest coexisted with dinosaurs

primates

mammals with:

- opposable thumbs

- flat nails instead of claws

- binocular vision, improved depth perception

- larger brain to body size

hominins

- developed from primates

- includes humans & human-like primates

australopithecus

the earliest humanlike creature

genus homo

- diverged from australopithecine line

- larger bodies & brains

- still ape-like: long arms, short legs

- used tools

homo erectus

- 1st species to leave Africa

- used tools

- spread through Asia

- went extinct due to unknown reasons

neanderthals

- left Africa, went to Europe

- DNA only .12% different from humans

homo sapiens

- modern humans

- last species left in Africa

evolutionary timeline of humans

1. primates

2. hominins

3. australopithecus

4. genus Homo

-- Homo erectus

5. neanderthals

6. Homo sapiens

taxonomy

branch of biology concerned with naming (based on genus and species) and classifying organisms

genus

a group of related, similar species

species

- within a genus, includes organisms that can potentially interbreed

- most specific category (~10 mil species on Earth today)

rules for scientific naming

- underlined or italicized

- 1st letter of genus ALWAYS capital

- 1st letter of species lowercase

- genus and species always in pair

taxonomic classifications

1. domain

2. kingdom

3. phylum

4. class

5. order

6. family

7. genus

8. species

domain

- broadest category (only 3 on Earth):

*eukarya

*bacteria

*archaea

domain eukarya

4 different groups:

- animals

- plants

- fungi

- protists

phylogenetics

- the study of evolutionary relationships among species

- diagrammed as "phylogenetic trees" or "evolutionary trees"

nodes

- the points at which stems of an evolutionary tree are attached

- represent speciation

clades

group of organisms believed to have evolved from a common ancestor, according to the principles of cladistics.

characteristics of prokaryotes

- smallest & simplest living things

- single-celled (cannot be seen w/naked eye)

- 3 common shapes: spherical, rod-shaped, spiral-shaped

- they live EVERYWHERE

- reproduce by binary fission

binary fission

- single bacterium replicates DNA then divides in half

- asexual cell division producing identical copies (sometimes w/mutations)

- can occur as often as every 20 minutes

- fast reproduction=fast evolution

conjugation

- exchange of genetic material between prokaryotes without reproduction

plasmid

- small, circular piece of DNA located in the cytoplasm of many bacteria

- separate from main chromosome

differences between bacteria & archaea

1. molecular & structural differences

2. archaea can produce methane

3. some bacteria (autotrophs) can undergo photosynthesis

- archaea = heterotrophs

4. some bacteria are pathogenic

5. bacteria contain peptidoglycan

- gram stains

6. some bacteria produce endospores or biofilms

heterotrophs

organisms that cannot make their own food

autotrophs

organisms that are able to make their own food

pathogens

disease causing agents

peptidoglycan

- layers carbohydrates linked by proteins

- forms a mesh-like layer around bacteria

- some bacteria also have an extra fatty layer covering

gram stains

- tells whether the peptidoglycan is on the outside or covered by the extra fatty layer

- gram positive = purple

- gram negative = pink/red (extra fatty layer)

biofilms

communities of slime-secreting bacteria

endospores

A thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions.

prokaryotes & nutrition

- prokaryotes in digestive system break down carbohydrates into absorbable nutrients and produce certain vitamins (B & K)

- promote immune system function

- killing of pathogenic bacteria

- breakdown of dietary carcinogens

prokaryotes & recycling

- break down complex organic molecules into basic building blocks that all organisms need

- they break down waste products & the dead bodies of plants & animals

prokaryotes & nitrogen fixation

- ~78% of our atmosphere = nitrogen

- all organisms need nitrogen: prokaryotes break down N2 into a useable form of nitrogen

prokaryotes & bioremediation

- some can clean up pollution

- a few human-made substances are biodegradable by certain prokaryotes

bioremediation

stimulating the breakdown of pollutants by living organisms

pathogenic prokaryotes

- some bacteria can cause illness & disease

- spread through: inhalation, insect bites, contaminated food/water, open skin, shared bodily fluids

non-living pathogens

viruses, viroids, prions

virus

- a molecule of DNA or RNA surrounded by a protein coat that holds their genetic material, not a cell

- not alive

- very small

- can & do evolve but do not maintain homeostasis

- require energy or nutrients

- can only reproduce with help

- are PARASITES

- attack all living organisms (prokaryotes, plants, fungi, protists, & animals)

viroids

- infectious particles with only short RNA strands (no protein coat)

- only affect plants

- effects on food supply

prions

- infectious proteins devoid of any genetic material

- extremely resistant to disinfection & sterilization

- 142 amino acids

- resistant to proteolytic enzymes

- survives dry heat

- cannot be destroyed

protists

- any eukaryotic organism that is NOT an animal, plant, or fungi.

- 3 categories: animal-like, plant-like, fungi-like

animal-like protists

move around & hunt for prey like an animal

fungi-like protists

live as heterotrophs & form sheet-like colonies of cells like a fungus

plant-like protists

multicellular & photosynthetic like a plant

areas of diversity among protists

1. single- v. multicellular

2. terrestrial v. aquatic

3. motile v. stationary

4. sexual v. asexual reproduction (binary fission)

5. heterotrophic v. autotrophic (or both=euglena)

heterotrophic protists

absorb nutrients directly through the cell membrane

predatory protists

- ingest food using pseudopods (extension of cell membrane) to surround & engulf prey

- some create tiny currents to sweep food particles into mouth-like openings

protists that absorb nutrients

- free-living: decompose organic dead matter

- parasitic: live inside an organism, sometimes harm host

protists & photosynthesis

- autotrophic protists provide about half the energy on Earth

- turn sunlight into fuel

- produce oxygen

- pull carbon dioxide from atmosphere

protists & food

- provide important food source for land & ocean organisms

- plankton are the most important organism on the ocean food chain

protists & commercial uses

- agar=derived from algae (used for a lot of things)

• vegetarian substitute for gelatin

• thickener for jellies, ice creams, & other

desserts

• clarifying agent for brewing

• thickener for toothpaste, paint, cosmetics

• base for vitamin & drug capsules

• culture medium for microbiology research

pathogenic protists

- cause plant & animal disease

- hard to treat illnesses caused by protists because they are eukaryotes--need to find ways to kill them without harming our own cells

- can infect important crops

- some marine protists release toxins (some release a nerve toxin that causes illness or even death in dolphins, seals, sea otters, fish, birds, humans, etc.)

Key features of fungi

- heterotrophic: secrete enzymes breaking down surrounding food molecules to absorb

- have chitin in cell walls

- multicellular (except yeast)

- reproduce using spores (except yeast,

- mycelium body structure (an interwoven

mass of threadlike filaments called hyphae)

- form important relationships with other organisms (endophytes, mycorrhizae, & lichen)

spores

- reproductive cells that grow when they land in a suitable habitat

- often rely on being carried through the

air or water

fruiting bodies

reproductive spore-producing structures such as mushrooms, puffballs, or truffles

endophytes

- live inside plants and take nutrients

- provide benefits to the plant:

increased growth

resistance to drought

protection against pathogens

protection from being eaten by insects &

other animals

mycorrhizae

- live in & around the roots of plants, taking some of the energy the plants make from photosynthesis

- In return, fungi secrete enzymes that break down large nutrients in the soil all around the roots, allowing the plant to absorb them

lichen

- fungi that live with photosynthetic protists or bacteria

- take some of the energy made from photosynthesis

- fungi provides an anchor & protection

- very diverse: grow on a wide variety of materials (soils, tree trunks & branches, leaves, rocks, fences, roofs, walls, & in water, etc.)

- can survive environmental extremes (newly formed volcanic islands, deserts, high altitudes, etc.)

fungi positives

- provide antibiotics, food, yeast for baking & brewing

- act as important decomposers

- create healthier environments through their symbiotic relationships

fungi negatives

- some fungi are parasitic & cause damage to hosts

- mold & mildew can destroy goods

- some fungi are poisonous

- some fungi are pathogenic

fungi & antibiotics

- not all, but many antibiotics are derived from fungi

- 1st antibiotic discovered, penicillin, is produced by a mold

- other medications are derived from fungi

fungi & food

- mushrooms, such as morels & truffles, are eaten by many animals

- certain molds impart flavor to some of the world's most famous cheeses (Roquefort, Gorgonzola, Brie, etc.)

yeast

- Wine is produced when yeasts ferment fruit sugars

- Beer is derived when yeasts ferment sugars in germinating grains (e.g. barley)

- Bread rises when yeasts ferment sugar that has been added to bread dough

fungi & decomposition

- Fungal saprophytes feed on dead organisms: secrete substances that digest the tissues of dead organisms, liberating nutrients that can be reused by plants

parasitic fungi

- fungal parasites cause the majority of plant diseases

- rusts & smuts = parasites that cause considerable damage to grain crops

mold & mildew

- can destroy goods

- some cause wooden structures to rot

- some damage cotton & wool fabrics

poisonous fungi

- Claviceps purpurea produces several toxins

(including LSD): infects rye plants & causes

a disease called ergot

ergot

symptoms of ergot poisoning = vomiting, convulsive twitching, hallucinations, & death

pathogenic fungi

- Athlete's foot, jock itch, & ringworm are caused by fungi that affect skin

- Most vaginal infections are caused by the yeast

Candida albicans

- Valley fever & histoplasmosis are caused by fungi

that affect the lungs

• infection occurs when the victim inhales

spores - can be fatal