Biology Exam 2: Origins of Life Flashcards
When did the first eukaryotes evolve?
1.5-2 billion years ago
What is used as an evolutionary proxy for early eukaryotes and why?
Living, single celled eukaryotes (protists) are often used as a proxy because the fossil record does not capture the evolution of these single celled euk. as clearly as we would like
monophyletic
sharing a single common ancestor
Prokaryotes v Eukaryotes cytoskeleton? Division? chromosomes? nucleus? organelles? size of cells? number of cells?
Prokaryotes // Eukaryotes
no cytoskeleton // have a cytoskeleton
binary fission // mitosis
circular chromosome // linear chromosome(s)
DNA not enclosed // DNA enclosed in nucleus
No organelles // membrane bound organelles
small // large
typically unicellular (biofilm) // often multicellular
Key evolutionary changes prok –> euk : (6)
- The loss of a firm cell wall
- Origin of a flexable cell surface
- Origin of a nuclear envelope
- Origin of digestive vacuoles
- Origin of mitochondria and chloroplasts by endosymbiosis
- Lateral gene transfer from bacteria and archaea
What had to happen for infolding of the plasma membrane? What did this change allow for (2)?
Loss of a firm cell wall.
- increased cell surface area for higher rates of gas and nutrient exchange
- Endocytosis
Endocytosis played a key role in the evolution of which 3 structures?
the nuclear envelope, membrane bound organelles, and the symbiosis with prokaryotes that produced the chloroplasts and mitochondria
Evolution of mitochondria:
Mitochondria originated as proteobacteria that entered the cell via encapsulation. the proteobacteria developed a symbiotic relationship with the early eukaryote because the mitochondria detoxified free oxygen within the cell
Evolution of chloroplasts:
Chloroplasts evolved via encapsulation of cyanobacteria and the secondarily encapsulated in a larger euk in different lineages. Differing chloroplast membranes in different lineages suggests this happened independently multiple times
The evolution of a cytoskeleton allowed for: (2)
- The physical support of a larger cell
2. The effective transport of material within the cell, including the equal split of DNA into daughter cells
What structure likely evolved from the microtubules found in the cytoskeleton?
flagellum, which allows for proficient propulsion and movement
What are protists or protista?
single celled eukaryotes. They are the most ecologically diverse of all eukaryotes.
Why are protists of great interest to biologists? (2)
- They can be used as an evolutionary proxy to examine the evolution of the first eukaryotes
- Protists are key members of the ecology of our planet, a few are important disease causing agents
Why are protists important in ecosystems?
- Protists include photosynthetic primary producers that are the base of many food chains and produce free oxygen
- many heterotrophic protists serve as a trophic bridge between bacteria and larger organisms
Do protists reproduce sexually or asexually?
Both. Asexual: binary fission, multiple fission, budding, and spores. Sexual: varies. One example is conjugation
Are fungi more closely related to plants or animals?
Animals
T or F: there are still areas of major phylogenetic uncertainty in the evolution of eukaryotes
T
Alveolates
Protists. large, diverse group having sacs (alveoli) under their plasma membrane. Many are typically photosynthetic with cellulose in their cell walls. Contains Apicomplexans (aka sporozoans), Dinoflagellates, and ciliates.
Apicomplexans (sporozoans)
Alveolates. Obligate parasites named for their mass of organelles contained in the apical tip of their cell. Can be extremely resistant to environmental changes such as temperature or bleach exposure, typically pass through different life history stages in different hosts. Example: Plasmodium (malaria)
Dinoflagellates
Alveolates. two flagella, one equilateral and one longitudinal. Important primary producers . Formed a symbiotic relationship with coral (dinoflagellate performs photosynthesis providing energy for the coral while the coral gives the protist somewhere to grow). Some are parasitic: “red-tides”
Ciliates:
Alveolates. known for their short, numerous flagella called cilia and two types of nuclei. Mostly free living but a few are parasitic. Aid in the digestion of cellulose in cows and termites
Diatoms
Stramenopile. Unicellular, photosynthetic protists that deposit silica (glass like) in their cell walls. Extremely important primary producers in salt and freshwater environments (account for ~20% of the Earth’s total photosynthetic and fix as much biomass as all of the terrestrial rainforests). Went through secondary endosymbiosis in the distant past –> energy production = key to group success.
Coccolithophores
stramenopile which builds a budding exoskelaton of CaCO3 to protect itself from predators. Sequestering of minerals in their shell is highly pH dependent and human ∆s to ocean pH have caused far more CO2 output from these organisms (form a CO2 molecule when they are made).
Brown Algea
Stramenopile. multicellular protist often attaining great size (kelp, seaweed). Important primary producers (food and habitat for other organisms)
oomycetes
Stamenopile. fungi-like absorptive heterotrophs. typically feed off dead organisms through filamentous outgrowths. Some are aggressive plant pathogens causing potato blight and sudden oak death
stamenopiles
Diatoms, Coccolithophores, brown algea, and oomycetes
Excavates
diverse group of single celled, non-photosynthetic organisms, several of which lack mitochondria. This is a derived condition (their ancestors had mitochondria). Euglenids, kinetoplastids, parabasalids, diplomonads, heteroloboseans
Diplomads
Excavate. unicellular protists which lack mitochondria. Include the disease organisms Giardia (one of the most common water born illnesses for humans and other mammals),
Parabasalids
Excavate. unicellular protists which lack mitochondria. Include the disease organisms trichomonas vaginalis.
Heteroloboseans
Excavate. group with two life history stages: one as a flagellated cell and then as an amoeba. Can have members that cause serious infections.
Euglenids
Excavate. distinctive cell surface produced by spiralling strips of proteins, disk-shaped cristae, and flagella with a unique crystalline rod. Common freshwater group. Some are strictly photosynthetic while others are heterotrophs.
Kinetoplastids
Excavate. contain disk-shaped cristae, and flagella with a unique crystalline rod. Typically parasites. Able to change their cell surface to avoid detection by the immune system. Examples: Chagas’ disease, Leishmanaisis, and sleeping sickness
Rhizaria
unicellilar, aquatic, and often have hair-like pseudopodia (a temporary protrusion of the surface of an amoeboid cell for movement and feeding). Can be found in marine or freshwater.
Foraminiferans
Rhizaria. have external porous shells made of CaCO3. Mostly planktonic and very numerous.
Radiolarians
Rhizaria. exclusively marine, many radially symmetrical, and secrete glassy endoskeletons covered in cytoplasm. Many radiolarians harbor other photosynthetic protists such as dinoflagellates.
Plantae
typically photosynthetic organisms, all aquatic with the exception of land plants. Appear to be monophyletic.
Glaucophyte
Plantae. Small group of unicellulat fresh water organisms. They are of special interest becasue they retain some ancestral traits eg. their chloroplasts retain a bit of peptidoglycan between their inner and outer membrane (typical of cyanobact.)
Red Algea
Plantae. marine photosynthetic multicellular organisms red photosynthetic (phycoerythin). Unique in having slightly ameboid male gametes
Chlorophytes
Plantae. morphologically diverse freshwater (a few can be marine or terrestrial) group. Referred to as green algae, posses chlorophyl a and b, store photosynthetic products as starch. Looked at as a proxy for how early plants began.
Unikonts
include fungi, animals, and slime molds. _____________
Opisthokonts
Unikont. Include animals, fungi, and choanoflagellates. All posses a posterior single flagella as opposed to multiple anterior flagella. Choanoflagellates often form colonies and these colonies are thought to be the origin of multicellularity/first animals
Amoebozoans
protists characterized by their thick pseudopods (fake feet) and amoeboid body morphology. Gain nutrients by phagocytosis.
Loboseans
amoebozoans. exclusively single celled organisms that live within a hard covering that is either secreted or glued together from sand grains. Slime molds are surprisingly diverse.
Plants can be divided into 2 broad groups:
green algae (including the most recent ancestors of land plants) and land plants
11 Ecological importances of plants:
- Production of O2 (50%)
- Grab CO2 from atmosphere
- Roots associated with N2 fixing bact.
- Hold water in soil and increase humidity
- Become soil –> nutrient source
- Hold soil, prevents erosion
- Stable climates an microclimates for animals
- Primary and secondary food for all animals
- Biofuel
- tools
- Medical compounds from plant chem
In plants, sunlight acts as an _______
energy source
CO2 is absorbed via the ______ in plants
stoma
Water from the soil is transported via the _______ in plants
xylem
______ transports sugars from the photosynthetic tissues (leaves) to other plant tissues (roots)
Phloem
Photosynthesis overview:
Equation
Summary
products and where they come from
6CO2 + 6H2O –> C6H12O6 + 6O2
Chlorophyl molecules, when struck by photons, change light energy into chemical energy. Results in sugars or other carbohydrates (starch) that are used in cellular respiration and O2 derived from the splitting of water
The calvin cycle is a _____ of the citric acid (Krebs) cycle and glycolysis
sort of reverse.
Calvin cycle takes in CO2 and energy and gives off sugars
Plants in the food chain:
primary producers. Responsible for 10,000 J of energy which results in 10J at the tertiary level. Energy transfers between trophic levels is very inefficient. Lots and many creatures consume at a primary level but it is better is a critter can successfully eat at the tertiary level (more energy per meal)
What organism is able to transform carbon and oxygen into usable forms? By what process?
Cyanobacteria and their relatives transform C and O into usable forms through primary production. This is the ultimate limiting reaction for life on our planet!!
What are plants’ relationships with terrestrial organisms?
Terrestrial organisms: ultimate source of energy for most organisms
What are plants’ relationships with fungi?
Fungi: forms mutually beneficial relationships with fungi. Plants rely on associations with fungi to increase the SA of their roots for absorption of water and nutrients from the soil by 10-1000X. Root+fungi form mycorrhizae. In this relationship, the fungi receive energy in the form of simple sugars from the plant. Mycorrhizae can also connect plants, allowing them to communicate and share resources.
What are plants’ relationships with bacteria?
Plants and bacteria form symbiotic relationships: not well understood, but it is believed bacteria keep other pathogens at bay in plants. Also allow nodules of N fixing bacteria to associate with plants, which is essential in the terrestrial eco (marine has aquatic cyanobact that can also perform N fixation)
Rice, wheat, maize, potatoes, manioc and sweet potatoes make up what % of our diet?
56% (56% from just 6 plants)
Bananas, soy beans, beans, sorghum, barley, coconuts, sugar cane and sugar beets make up ___% of our diet
14%
14 plants make up ___% of human caloric intake
70%
What is the most important eukaryote in human survival?
Rice. Responsible for 20% of human caloric intake.
Artificial selection in corn:
Artificial selection in plants dates back at least 10,000 years. Corn was selected for larger kernels without a tough covering, leading to a v important food crop. Recall wild mustard example of art selection
Uses of Cannabis:
structural material (grows quickly, strong but pliable), psychoactive, medical research/treatment
What percentage of plants have been investigated for medical purposes?
2%. The worry is that these rare plant species will go extinct or we will kill them before they’re discovered and utilized.
Dust bowl:
We ripped out plants from the soil and when the drought hit, dust ensued. Lost a yard of soil in 2 years. It takes 1,000 years to make 1 inch of good soil
Plants and CO2: sink or source? Are some plants better than others?
Both, but they are a net sink because their tissues take so long to break down. Trees are the best carbon sinks because of their ability to hold massive amounts of carbon for a long period of time. Fast growing weedy species release ~ as much C as they take in.
What is the main source of increasing atmospheric CO2?
The burning of fossil fuels ie. coal, petroleum, and natural gas.
What is a common misnomer regarding climate change and food supply?
That we can simple move human habitation and farming. This is not the case as heating places makes it hard to grow food and some places just have bad soil.
What countries are experiencing deforestation and which are attempting reforestation?
Deforestation: S. America, Africa, Asia
Reforestation: Some parts of North America and Europe
From what organism did plants evolve and when?
Plants evolved from aquatic green algae approximately 500 million years ago. Adaptations occurred for living on land versus in water
Nonvascular plants:
Bryophytes. Include liverworts, mosses, hornworts. Bryophytes are small, often living on marginal areas, and many ancestral features:
- No true leaves, stems, roots, or vascular tissues
- Need moist areas
- Ancestral alternation of generation pattern
Seedless vascular plants:
Ferns: First vascular plants lack leaves, roots, and seeds (425 MYA). leaves and roots evolved in later ferns. Did have vascular system and simple roots allowing for vertical growth. Require a wet environment for reproduction so sperm can swim to eggs.
Seed Vascular plants
Gymnosperms and Angiosperms
Gymnosperms
Seeded vascular plants (naked seed). evolved 300 MYA. Novel feature of male “spores” that spread by wind rather than water and female eggs “seeds” are covered in a tough coat to resist dehydration and damage.
Had evolutionary traits that better adapted them to land:
1. woody stem, secondary growth leading to larger size
2. thicker waxy cuticle covering the leaves to prevent H2O loss
3. larger root system for support
Angiosperms
Seeded vascular plants (covered seed) origin 150 MYA. Flowering plants and diversified to become the dominant terrestrial eukaryotes ~75 MYA. A major diagnostic feature of angiosperms is double fertilization. Only plants w true flowers, most abundant plant species on the planet.
Double fertilization:
Occurs in angiosperms. Male gamete carries two sperm, one of which fertilizes the egg and becomes the offspring while the other fertilizes two other haploid nuclei of the female and form a 3n nucleus and tissue which grows and divides to nourish the primary embryonic tissue
What factors contribute to the evolutionary success of angiosperms?
- More efficient vascular system
- supportive fibers in the xylem
- phloem companion cells
- novel structures associated with reproduction: Flowers and fruit
- Coevolution with animals(for pollination or dispersal of the seeds. Most commonly seen with arthropods, specifically insects. insect diversity and angiosperm diversity increased rapidly at the same time)
What are flowers and fruit in angiosperms?
Flowers: derived leaf structures. they house reproductive structures and are often shaped to attract particular animals
Fruit: derived from differing parts of the flower structure. Encase the fertilized egg or seed. Disperse seeds in a variety of ways (consumed, in animal fur, wind)
Example of coevolution of arthropods and angiosperms:
The flower that looks like the wasp. Male wasps will try to have sex with it. This does not hurt or benefit the wasp, but it aids in pollination/dispersal for the plant.
Linnaean rediscovery regarding plans:
That plants could reproduce sexually. Produced a scandal in Europe.
Perfect: one flower, both sexes (monoecious)
Imperfect: one sex per flower (dioecious)
Alteration of generations trend (sporophyte v gametophyte)
the more ancestral plants tend to spend more of their life in the haploid phase. more derived plants spend more time in the diploid phase. The exact amount of time spent in sporophyte (diploid)/gametophyte (haploid) phase varies across taxa.
sporophyte
diploid, 2n
gametophyte
haploid, 1n
Three main evolutionary problems for plants:
- Plants can not move away from predators like animals can.
- infection from fungi, bacteria, and viruses.
To combat these, plants often have tough outer coverings or utilize chemical compounds typically formed as metabolic byproducts.
4 main themes behind plant evolution:
- limiting water loss
- structural support in the form of roots and form woody material for vertical and horizontal growth
- a system of transport within the plant (vascular system)
- Reproduction and dispersal
NOTE: these are the same themes faced by animals as they leave water to adapt to land
How any species can you fit in 10 sq miles?
- However, doubling the land area does not double the number of species. In order to get 2x the species, you would have to have 10x the land.
What role to kelp forests play in conservation?
Foster diversity of species (read up more on this)
Keystone or engineer species
species that occur in low numbers and biomass that still have an enormous effect on the ecosystem. (II ch 58)
keystone species
species with a relatively low biomass but have an enormous impact on the ecosystem (ex: kelp)
Mycology
the study of fungi
What special function does fungi perform for breakdown in terrestrial ecosystems other plants/animals can not do?
Fungi break down cellulose and lignin, cycling the nutrients locked up in these structures back into the ecosystem. Digestion of large molecules os accomplished externally by fungus.
Are fungi more closely related to plants or animals?
animals
What percentage of terrestrial respiration is each group responsible for?
25% fungi
25% plants
50% microbes
<1% animals
Why is our knowledge of fungi relatively limited?
There is simply too much diversity for us to even grasp. Conservative estimates arrive at 1.65 million fungi species.
General fungal structure:
“body” of fungi are long thin multicellular net-like fibers with almost no definable features. Many are spherical and single celled (yeasts) and some species adopt both forms depending on ecological conditions
Mycelia
Mycelia: the vegetative part of a fungus, consisting of a network of fine white filaments
Hyphae
the individual strands of the mycelia. cells walls of the hyphae incorporate chitin in cell walls. Individual cells of the hyphae are separated by septa.
rhizoids
hyphae that serve as physical anchors to substrates
coenocytic cells
species that lack septa and have dozens or hundreds of nuclei within a hyphae. results from nuclear division without cytokinesis
what % of soil biomass is fungi?
25%
What conditions can fungi live in?
Fungi are tough, they can handle extremes in pH and temperature, but they can not survive in DRY climates
How do fungi break down lignin? (enzyme)
Saprophytic (gets its energy from dead organisms) fungi produce lignin peroxidase that removes an electron from the ring structures of lignin which then react with other bonds within the molecule further breaking it down.
Describe fungal reproduction
fungi have great diversity in their reproductive strategies making complete summary difficult. Overview:
- Both sexual and asexual strategies
- fungi have no “gender” but many reproductive types
- commonly use spores to reproduce because they can resist environmental extremes
- alt of generations
names for parasitic fungi (4)
blights, rusts, smuts, rots
Two plant adaptations as defense against parasitic fungi:
physical and chemical defenses. Thickened areas and secondary compounds
haustoria
parasitic fungi that are able to invade plant cells but do not puncture the plasma membrane allowing them to absorb cellular material without killing the cell
predacious fungi
consuming live animal prey is very rare for fungi but not unheard of. Typically, the fungi excretes a sticky liquid that traps a small organism but some grab their prey. fungi can kill its prey by growing from the inside out after being consumed or the outside-in.
Why are fungal infections difficult to treat chemically in humans?
Because fungi and humans are so closely related evolutionarily, anything chemical that would hurt the fungus will most likely hurt the human too. We treat fungal infections, we don’t typically cure them. Two common fungal infections in humans: candidiasis (thrush) and athlete’s foot
Lichens
facilitated formation of soil millions of years ago and today. Made up of fungus and a mutualistic photosynthetic organism, either a bacteria or a protist. Photosynthetic cells imbed in fungal mycelium to provide E and C. Lichens are sensitive to toxic compounds and are good indicators of air pollution.
