Exam 2 Flashcards
Ecological Species Concept
defines a species by its ecological niche; applies to sexual and asexual species and emphasizes the role of disruptive selection
Macroevolution
-broad patterns of evolutionary change above the species level
-cumulative effect of many speciation and extinction events
Speciation
the process by which one species splits into 2 species
What does speciation contribute to biology?
-produced tremendous diversity of life
-helps to explain the unity of life
-forms a conceptual bridge between micro- and macroevolution
Temporal Isolation
species that breed at different times of day, in different seasons, or different years –can’t mix their gametes
Microevolution
changes in allele frequencies in a population over time
Behavioral Isolation
-prezygotic barrier
-courtship rituals and other behaviors unique to a species are effective barriers to mating
Biological Species Concept
-have the potential to interbreed in nature
-produce viable, fertile offspring
-don’t produce viable, fertile offspring with members of other such groups
Reproductive Isolation
-when biological barriers impede members of 2 species from interbreeding and producing viable, fertile offspring
-limits the formation of hybrids
Habitat Isolation
-prezygotic barrier
-two species that occupy different habitats within same area may encounter each other rarely, if at all
What was early life on Earth like?
-inhospitable
-little to no oxygen in atmosphere
-meteorite impacts and volcanic eruptions common
-seas full of mineral salts
Gametic Isolation
-prezygotic barrier
-sperm of one species may not be able to fertilize eggs of another species
Prezygotic Barriers
-block fertilization from occurring by impeding different species from attempting to mate
-preventing the successful completion of mating
-hindering fertilization if mating is successful
Mechanical Isolation
-prezygotic barrier
-mating attempted, but morphological differences prevent its successful completion
Postzygotic Barriers
-prevent hybrid zygotes from developing into viable, fertile adults
Reduced Hybrid Variability
-genes of different parent species may interact in ways that impair the hybrid’s development or survival in its environment
Reduced Hybrid Fertility
Meiosis may fail to produce normal gametes, resulting in sterility if the parent species have chromosomes of different number or structure (i.e. mules)
Hybrid Breakdown
First generation of hybrids are viable and fertile, but offspring in the next generation are feeble or sterile
What are the limitations of the Biological Species Concept?
-cannot be applied to fossils or asexual organisms (including all prokaryotes) because mating can’t be observed
-emphasizes absence of gene flow, but gene flow occurs between many morphologically and ecologically distinct species (i.e. grizzly bears + polar bears = grolar bears)
Morphological Species Concept
-distinguishes a species by its structural features
-applies to sexual and asexual species, doesn’t require info on the extent of gene flow
-Disadvantage: relies on subjective criteria
Allopatric Speciation
-gene flow restricted between populations by geographic isolation
-intrinsic barriers to reproduction due to genetic change driven by processes including divergent selection and genetic drift
-reproductive barriers prevent interbreeding even if contact restored
Sympatric Speciation
-reproductive barrier isolates subset of populations without geographic separation
-result from polyploidy, sexual selection, or natural selection resulting from switch in food or habitat
What are the two types of polyploidy?
Allopolyploids and Autopolyploids
Autopolyploidy
-have more than 2 sets of chromosomes from a single species
-in plants, mitotic errors can result in production of tetraploid cell from diploid cell
-fertile offspring produced through self-fertilization or mating with other tetraploids
-mating between tetraploids and diploids produces triploid offspring with reduced fertility
Allopolyploidy
-have 2 sets of chromosomes from different species
-don’t pair during meiosis, resulting in hybrid sterility (sterile hybrids can reproduce asexually)
-formed if chromosome number doubles in subsequent generations
-successfully interbreed with each other but not with either parent species
-diploid number of new species = sum of diploid number of both parents
Habitat Differentiation
-sympatric speciation can result from exploitation of new habitats or resources
example: apple maggot flies evolved after switching hosts from hawthorn to apple
Hybrid Zones
-a region where members of different species mate and produce hybrid offspring
-some hybrid zones form as narrow bands where habitats of 2 or more closely related species meet
-often occurs as isolated patterns scattered across landscape rather than continuous band
How does environmental change affect hybrid zones?
-changing environmental conditions can cause them to relocate
-can also drive production of new hybrid zones
-alleles can be transferred from one parent species to the other through breeding between parents and hybrids (may help parent species cope with changing environments)
What happens if hybrids don’t become reproductively isolated from their parent species?
Reinforcement, Fusion, or Stability
Reinforcement
-strengthening reproductive barriers
-if hybrids are less fit, strong selection for prezygotic barriers should reduce hybrid population
-should be stronger for sympatric than allopatric populations
Fusion
-weakening reproductive barriers
-there can be substantial gene flow between species if hybrids are as fit as parents
-reproductive barriers can weaken and 2 parent species may fuse into a single species
Stability
-continued formation of hybrid individuals
-extensive gene flow from outside hybrid zone can overwhelm selection for an increase in reproductive isolation inside hybrid zone
Punctuated Equilibria
-periods of apparent stasis punctuated by sudden change found in the fossil record
-other species appear to have changed gradually over time
Average time of speciation
6.5 million years
What do all cells have?
-enzymes (carry out reactions)
-plasma membrane
-genome of DNA
Protocell
-believed to be predecessor of cells
-membranous sac containing interacting organic molecules
What was the dynamic between RNA and DNA originally?
-RNA may have preceded DNA
-RNA was THE genetic material and dominant
-switching from RNA to DNA would’ve made genome more stable
Ribozymes
-RNAs that act like enzymes
-support the idea of RNA being dominant genetic material at first
Cyanobacteria
-evolutionary bacteria; first to release oxygen through photosynthesis
-over time, oxygen released by cyanobacteria changed earth’s atmosphere
What did the addition of oxygen do to Earth?
-created the ozone
-favored aerobic life forms
-beginning of ATP-forming metabolic pathway (key innovation in evolution of eukaryotic cells)
First Eukaryotes
-Protists
-proven by their biomarkers and fossils dating back more than 2 billion years
-their diversification led to plants, fungi, and animals
Eukaryotes
-defined by having membrane-enclosed organelles
-some probably evolved from infoldings of plasma membrane in prokaryotic ancestors
-mitochondria and chloroplasts resemble bacteria; maybe evolved through endosymbiosis
Endosymbiosis
-an evolutionary process where one cell enters and survives in another cell
-over generations, host and guest cells begin to depend on each other for essential metabolic processes
-proof: modern protists who have bacterial symbionts inside them
Bacteria
-small cells with DNA and ribosomes
-no nucleus or typical eukaryotic organelles
-most abundant and metabolically diverse organisms
-autotrophs and heterotrophs
-most are unicellular, though some species form colonies
Autotroph
-bacteria that self-feed
Heterotroph
-bacteria that feed on others
What are the three most common prokaryotic cell shapes?
-cocci (spheres/ellipses)
-bacilli (rods)
-spirillus (spirals)
What’s special about bacterial cell walls?
-they contain peptidoglycan, a network of sugar polymers crosslinked by polypeptides
Gram Stain
helps scientists classify many bacterial species into Gram-positive and Gram-negative groups based on cell wall composition
Gram-Negative Bacteria
-less peptidoglycan and an outer membrane that can be toxic
-have thin cell walls
-stain pink/red
-more likely to be antibiotic resistant because they target peptidoglycan
Gram-Positive Bacteria
-thick cell walls
-stain purple/blue
What shape are prokaryotic chromosomes?
Circular
Plasmid
-small ring of nonchromosomal DNA replicated independently of the chromosome
Describe typical prokaryotic DNA
-a ring of DNA not surrounded by a membrane, located in nucleoid region
Binary Fission
-a type of asexual reproduction in bacteria
-divides 1 bacterial cell into 2 identical descendant cells
-can divide every 1-3 hours
Endospores
-a tough, nonreproductive spore that’s metabolically inactive
-can remain viable in harsh conditions for centuries
Are mutations in binary fission common?
No, but when they happen they can accumulate rapidly in a population due to rapid reproduction
Conjugation
-gene exchange in bacteria
-occurs when one cell passes a plasmid to another
Phototrophs
-obtain energy from light
Chemotroph
-obtain energy from chemicals
Autotrophs
-require carbon dioxide as a carbon source
Heterotrophs
-require an organic nutrient to make organic compounds
Lactobacillus
-lactate fermenter
-spoils milk
-used to make yogurt, cheese, sauerkraut, sour foods
-common decomposer
-L. acidophilus is part of flora on our skin, in gut, and vagina–lowers pH and keeps pathogenic bacteria in check
Clostridium tetani
-Gram-positive bacterium
-can form endospores
-endospores germinate in wounds and cause tetanus (toxins produced lock muscles in an ongoing contraction)
Bacillus anthracis
-produces endospores
-inhale endospores and you get anthrax (toxins produced interferes with your breathing)
Clostridium botulinum
-Gram-positive
-forms endospores
-anaerobic
-grows in improperly canned food
-produces toxin caused botulism (same toxin, botox, temporarily paralyzes face muscles)
Mycobacterium tuberculosis
-causes tuberculosis
–1/3 of world population has it
–bacterium is spread via cough droplets
–kills 1.6 mil people each year
Streptococcus
-causes strep throat
-also spread via cough droplets
-if bacterium gets into open wound can become flesh eating bacteria
–results in a fast-spreading infection that kills surface tissue and can result in death
Thermus aquaticus
-discovered in a volcanic spring in Yellowstone National Park
Spirochetes
-small group
-6 genera
-most live in cattle guts
-others are decomposers and nitrogen fixers
-major impact on our lives (syphilis and lyme disease)
Parasitic chlamydias
-tiny cocci
-live and replicate in eukaryotic host cells
-most common sexually transmitted bacterial disease in US
Cyanobacteria
-photosynthetic
-produce oxygen during photosynthesis
-carry out nitrogen fixation using atmospheric nitrogen to produce ammonia that plants and algae can use
-Spirulina, Anabaena, Oscillatoria, and Nostoc
Proteobacteria
-largest bacterial lineage
-includes nitrogen fixers
-includes soil bacteria that show cooperative behavior
-closest relatives of mitochondria
-cells that are a part of our normal flora
-some are pathogens
Rhizobium
-soil bacterium
-forms associations with the roots of plants
-fixes atmospheric nitrogen for its own use and the use of other plants
Myxobacteria
-soil bacterium
-exhibit cooperative behavior (work together to move around and feed on other bacteria)
-when food is scarce, thousands of cells get together to form a fruiting body (spores are produced and dispersed by wind)
Thiomargarita namibiensis
-largest known bacterium
-marine
-stores nitrogen and sulfur on a huge vacuole
-makes it easy to see with the naked eye
Escherichia coli
-lives in the mammalian gut (part of our normal flora)
-most E. coli benefit their host by producing vitamin K
-strain E. Coli 0157:H7 causes food poisoning
Heliobactor pylori
Causes ulcers
Vibrio cholerae
Causes cholera
Archaea
-discovered relatively recently
-many adapted to life in very hot/very salty environments
-some live in low oxygen environments making methane
-share certain traits with bacteria and others with eukaryotes
-none cause human disease
Extremophiles
Archaea that live in extreme environments
Extreme halophiles
Archaea living in highly saline environments
Extreme thermophiles
Archaea thriving in very hot environments
Methanogens
Archaea living in swaps and marshes and producing methane as a waste product
-methanogens are strict anaerobes and poisoned by oxygen
Methanococcus jannaschii
-First organism of kingdom Archaea to be completely sequenced in 1995
-its genome structure finally provided solid support for hypothesis that Archaea is a separate domain than Bacteria and Eukarya, but more closely related to Eukarya
-Archaeans co-exist with bacteria in many habitats and can exchange genes with them
What is a protist?
-A eukaryotic organism that is not a fungus, plant, or animal
-includes single-celled and multicellular autotrophs and heterotrophs
-don’t have much in common with each other besides simple cellular organization (distinguishes them from other groups)
What are the types of unicellular protist lineages?
Flagellated protozoans, shelled cells called foraminiferans and radiolarians, alveolates, ciliates, dinoflagellates, and apicomplexans
What do all flagellated protozoans have?
-single cells
-no cell wall
-protein covering called a pellicle helping cells maintain shape
-possess multiple flagella
What do diplomonads and parabasalids have in common?
-Flagellated protozoans
-no mitochondria
-both groups include human pathogens
-free-living ones thrive in deep seas and lakes, while others live in bodies of animals (including humans)
Giardia lamblia
-diplomonad (type of FP)
-has 2 essentially identical nuclei
-water borne human disease
-attaches to the intestinal lining and sucks out nutrients
-infected people and animals excrete cysts (Hardy resting stage)
- drinking cyst-infected water spreads the infection
-symptoms include cramps, nausea, and severe diarrhea
Trichomonas vaginalis
-parabasalid (type of FP)
-infects human urogenital tract (causes trichomoniasis)
-can’t survive very long outside body
-passed through sexual intercourse
-6 mil in US infected
Trypanosomes
-type of flagellated protozoan
-long tapered cells
-one large mitochondrion
-flagellum encased in a membrane running length of organism (causes wave-like motion in membrane that moves cell)
-all are parasites and insects are the vectors for human disease
Types of trypanosomes
-Tseste flies carry the one that causes African sleeping sickness (sub-Saharan Africa, can be fatal)
-Blood sucking bugs in Central and South America transmit the one that causes Chagas disease (16 to 18 mil people, damages the heart)
-Desert sandflies are the vector for leishmaniasis (can harm liver and produce disfiguring scars)
Euglenoids
-type of FP
-typically live in freshwater
-flagellated
-have a contractile vacuole that squirts out excess water
-have both plant and animal characteristics (chloroplasts and hunters)
Mineral-Shelled Protozoans
-two related lineages of heterotrophic marine cells
-have porous secreted shells
-foraminiferans and radiolarians
Foraminiferans
-single cells
-marine
-sieve like shell
-calcium carbonate shells
-chalk and limestone made of their remains
-benthic
-prey on bacteria and smaller protists on the ocean floor
-others are planktonic (plankton drift or swim in water column)
–planktonic forams often have photosynthetic protists living inside
Radiolarians
-secrete a glassy silica shell
-major component of the marine plankton in tropical waters
-some have photosynthetic protists living inside
Alveolates
-single cells
-possess membrane-bound sacs called alveoli under their plasma membrane
Dinoflagellates
-name means “whirling flagellate”
-single cell
-two flagella: one at tip and one running in a groove around its middle
-combined action causes cell to rotate as it moves forward
-heterotrophic and photoautotrophic
-have cellulose plates
-vast majority are marine plankton
-photosynthetic ones live inside reef-building corals
-some are bioluminescent
-some cause algal blooms called red tides
Ciliates
-heterotrophic
-cilia cover all or part of cell surface (function in movement and feeding)
-aquatic
-predators and parasites
-some adapted to living in animal gut
-trichonympha (termite gut), paramecium, stentor, and vorticella
Apicomplexans
-intracellular parasites
-spend part of life cycle living in hosts
-complex of microtubules at top end that let them pierce and enter host cell
-sometimes called sporozoans
-infect worms, insects, and humans
-life cycle often involves more than one host species
Plasmodium
-apicomplexan
-causes malaria
-leading cause of human death (more than 1.3 mil each year)
-mosquitoes carry the protist from one human host to another
Describe the plasmodium life cycle.
Infected mosquito bites human, sporozoites enter the blood and are carried to the liver. Once there, they reproduce asexually. When they mature into merozoites they leave the liver and infect red blood cells. In some of the cells they reproduce asexually, and in others they differentiate into gametocytes. A female mosquito bites and sucks blood from an infected human. Gametocytes in blood enter her gut where they mature into gametes. Gametes fuse to form zygotes, then meiosis produces cells that develop into sporozoites, who then migrate to mosquito’s salivary glands. Bites human and cycle starts again.
Stramenophiles
-apicomplexan
-include diverse lineages that are united on the basis of their genetic similarity, not visible traits
Water molds
-filamentous decomposers and parasites
-grow as a mesh of absorptive filaments
-some are important plant pathogens
Diatoms
-apicomplexan
-silica-shelled cells
-shell has 2 parts (upper and lower that fit together like shoebox)
-photosynthetic
-contain the pigment fucoxanthin
Diatomaceous Earth
-pool filters, toothpaste, fleapowder
Brown Algae
-multicellular
-photosynthetic (contain fucoxanthin)
-found in temperate seas
-include microscopic species and the giant kelps
-source of algins (thickeners and emulsifiers)
Red Algae
-belong to the same clade as the land plants
-multicellular
-marine
-cell walls of cellulose
-photosynthetic (use pigments phycobilins)
-can photosynthesize even in deep waters
-store excess sugars as starch
-commercially important
-source of agar (used in gelatins and desserts)
-carrageenan (used in cooking to make things gel)
-nori for sushi
Green Algae
-includes unicellular, colonial, and multicellular
-cell walls of cellulose
-photosynthetic (chlorophylls a and b)
-stores excess sugars as starch
-freshwater
-marine
-soil
-air
-some form partnerships with fungi (lichens)
-life cycle has alternation of generations
What common characteristics do red algae, green algae, and land plants share?
-cell walls of cellulose
-excess sugars stored as starch
-chloroplasts that evolved from a cyanobacterial ancestor
-descended from a common ancestor
-closest relatives is a group of green algae: charophyte algae
Amoebozoans
-heterotrophic no cell wall or pellicle
-can constantly change shape
-amoebas
-slime molds
Slime Molds
Single Cells (cellular slime molds)
-freshwater habitats
-predators
-guts of animals incl humans (most do no harm, few are pathogenic)
-aggregate into one giant mass = plasmodial slime mold
-form fruiting bodies that release resting spores
