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120 Cards in this Set
- Front
- Back
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First key innovation that was purely humanistic |
Bipedalism - Lucy, 3.2 million years ago, fully bipedal, Ardi, 4.4 million years ago, partially bipedal |
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Why did hominins become fully bipedal? |
Hands freed up - allowed for specialized hand function, ability to carry things over long term distances - complex foraging strategies, human jaw development |
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Human opposable thumbs |
3 muscles not present in chimpanzees, finer motor control of the thumb - as a byproduct of bipedalism |
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Anatomical changes in shift to bipedalism |
Foramen magnum balanced vertically above vertebral column, spine S-shaped, pelvis as basin for organs, longer legs, foot narrow and more arched |
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Neoteny |
Long-term evolutionary process in which the timing of development is altered so that a sexually mature organism still retains the physical characteristics of the juvenile form |
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Most significant evolution along the hominin lineage... |
Changes in gene regulation |
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Characteristics adult humans share with juvenile chimpanzees |
Larger heads (with larger brains), lack of hair, position of foramen magnum, mentality |
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Factors promoting large brain |
Natural selection, tool use (requires complex nervous organization), social living (coordination and communication necessary), language (chicken and egg situation) |
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Human brain - what evolved? |
Reorganization of existing structures and pathways, brain rewired |
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FOXP2 importance |
Gene is highly conserved, but changes with orangutan and twice with neanderthal-human |
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Why are humans so phenotypically different? |
Large genome, so even a small % variation is significant |
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When did populations of Homo sapiens leave Africa? |
60,000 years ago |
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What does this number mean? |
There are more genetic variations among the African population than among any other population - greater time for mutations and whatnot to present |
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Minor genetic differences among different races |
1. Hair color 2. Facial form 3. Skin type - only 7% of genetic variance - overrepresented - 85% genetic variation in human population occurs within a race |
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Why are visible traits so different among races? |
Natural selection - dark skin in lower levels of solar radiation while light skin in higher levels - heavily pigmented skin prevents UV radiation and vitamin D - not an issue with highly sunlit areas but an issue with areas with less sunlight Sexual selection - operates on visible characteristics |
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G6PD |
A gene that when heterozygous for a mutation results in severe anemia when fava beans are consumed - but also results in increased resistance to malaria - beneficial only in areas where malaria is prevalent |
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Carbon cycle |
Intricately linked network of biological and physical processes that shuttles carbon among rocks, soil, oceans, air, and organisms - interactions that underpin ecology and promote biological diversity |
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How is CO2 added to the atmosphere? |
1. Geologic inputs - volcanoes and mid-ocean ridges 2. Biological inputs - repiration 3. Human activities - deforestation and the burning of fossil fuelskk |
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How is CO2 removed from the atmosphere? |
1. Geologic removal - chemical weathering of rocks 2. Biological removal - photosynthesis |
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Photosynthesis reaction |
6CO2 + 6H2O -> C6H1206 + 6O2 |
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How much carbon is removed from the atmosphere by photosynthetic organisms per year? |
190 billion metric tons |
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How much of this carbon is removed by land plants? |
60%, the rest by phytoplankton and seaweed in the ocean |
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% annual photosynthetic removal of total CO2 in atmosphere |
25 |
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What makes atmospheric CO2 levels oscillate seasonally? |
High rates in summer because more photosynthesis occurring, low rates in winter because plants are dead |
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How much CO2 was in the atmosphere 1,000 years ago? |
Samples of glacial ice varied very little between 1000 and 1800, falling between 270 and 280 ppm, began increasing after 1800s |
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What kind of experimental relationship is this? |
Correlation - not causation |
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How do we know for sure that the increase in carbon is due to fossil fuels? |
Carbon isotope studies - C13:C12 ratio declining - volcanoes emit a higher ratio so they are not the cause - organic matter has such a small ratio on the other hand, C14 declining - modern organic matter has a lot of C14 while ancient organic matter (fossil fuels ) do not |
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Where does the CO2 generated by humans end up? |
About half in the atmosphere, the rest in oceans or in vegetation and soil |
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Primary producers |
Generate organic compounds that will provide food for other organisms |
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Consumers |
Obtain the carbon they need from the foods they eat |
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Decomposers |
Break down dead tissues |
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Food chain |
Linear transfer of carbon from one organism to another |
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Food web |
Provides a better sense of the complexity of interactions within the carbon cycle |
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Trophic pyramids |
Depict amount of energy available at each level, only about 10-15% of the energy available in biomass at one level gets incorporated to the biomass at the next level |
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Immense diversity of photosynthetic organisms |
Structural and physiological adaptations |
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Oxygen levels on earth... |
Did not increase to levels humans could breathe until 580 million years ago - enabled aerobic respiration |
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Prokaryotic domains of microscopic organisms |
Bacteria and archaea |
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Bacteria features different from eukaryotes |
No membrane-bound nuclei, no energy-producing organelles, no sex, nonetheless bacterial cells outnumber eukaryotic cells |
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Bacterial cell DNA |
Present as a single circular chromosome |
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Plasmid |
A small circle of DNA that replicates independently of the cell's circular chromosome - have adaptive value |
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Cell wall |
Provides structural support, comprised of peptidoglycan (complex of sugars and amino acids) |
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Types of cell walls |
Thick walls made up of multiple petidoglycan layers or thin walls surrounded by an outer lipid layer |
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Diffusion |
Process through which CO2 gets through photosynthetic bacteria - goes from region of high concentration to that of low concentration - why bacterial cells need to be small |
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How do large cells get past the diffusion-size limit |
Volume taken up by a vacuole, so metabolically active cytoplasm is still small (T. nambiensis) |
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Multicellular bacteria and myxobacteria |
mc - form filaments or sheets of cells, m - form multicellular reproductive structures composed of different cell types |
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Benefit of streamlining of bacterial genome |
Reproduction can occur rapidly |
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Horizontal gene transfer |
Major source of genetic diversity in bacteria |
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How is horizontal gene transfer accomplished? |
1. Conjugation - pilus provides migration route between two bacteria for direct cell-cell transfer of DNA - genes conferring antibiotic resistance 2. Transformation - DNA released into the environment by dead cells is taken up by a recipient cell (how harmless bacteria strains turn virulent) 3. Transduction - occurs by means of viruses |
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Archaea specifics |
Prokaryotic, limited cell size, membranes made up from lipids different from fatty acids in bacteria and eukarya, diversity of molecules in cell walls (no peptidoglycan or cellulose and chitin), DNA transcription involves RNA polymerase and ribosomes more eukaryote like than bacteria like, antibiotics ineffective against, inhabit extreme environments, may be most abundant organisms in the sea |
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Microbial mats |
Densely packed communities of bacteria and archaeons that thrive where animals and seaweed cannot grow |
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Layers of microbial mats |
Top is dominated by cyanobacteria (photosynthetic) using water as electron donor, CO2 still used by organisms deeper in the mat - bright purple or green and anoxygenic |
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Anoxygenic photosynthesis |
Harvest light energy but do not get electrons from water and thus do not produce O2- bacteriocholorophyll is present- one photosystem is only employed, use electron donors like hydrogen sulfide, H2, Fe2+, AsO33- |
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Can organic molecules be synthesized by heterotrophs in the absence of oxygen? |
Yes; oxidized forms of NO3-, SO42-, Mn4+, Fe3+, AsO43- can be used as electron acceptors in cellular respiration |
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Fermentation |
Provides an alternative to cellular respiration, partial oxidation of carbon compounds, no external electron acceptor required but less energy obtained, widespread in bacteria and archaea |
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Where does fermentation often occur? |
Oxygen poor environments that are rich in organic matter - landfills, digestive tracts of animals |
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Photoheterotrophs |
Organisms that rely on organic molecules obtained from the environment as the source of carbon for growth and other vital functions - advantageous in environments rich in dissolved organic compounds - types of bacteria |
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Chemoautotrophs |
Obtain energy to fuel process of reducing CO2 to carbohydrate, from chemical reactions |
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Chemoautotroph common electron acceptors and common electron donors |
Acceptor: O2, NO3 Donor: H2, H2S, Fe2+ |
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Where do chemoautotrophs generally live? |
Interface between oxygen rich and oxygen poor environments - requires access to oxidized and reduced molecules |
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Ability to use inorganic sources of energy is solely __________________ in nature |
prokaryotic; only bacteria and archaea can carry this out |
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How are bacterial species characterized? |
- By DNA sequences, genes of rRNA particularly - must be more than 97% identical - Or by telling which populations go through the same episodes of periodic selection |
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Periodic selection |
Episodic loss of diversity |
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SAR11 |
Heterotrophic bacterium, makes up a third of all sequences in the ocean surface |
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Proteobacteria |
Most diverse of bacterial groups, include organisms that populate our expanded carbon cycle and other biogeochemical cycles - some beneficial to humans (soybean nitrogen fixation) and others detrimental (typhus and cholera) |
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Gram positive bacteria |
Have thick peptidoglycan walls - for a well defined branch of the bacterial tree |
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Western children bacteria |
Firmicutes |
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African children bacteria |
Bacteroidetes |
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Why does this matter? |
May relate to the prevalence of allergies in the western world |
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Cytoskeleton |
Internal scaffolding of proteins, to organize the cell - can be remodeled quickly, enabling cells to change shape - new possibilities for movement |
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Endocytosis |
Particles are transported into the cell |
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Exocytosis |
Waste is expelled from the cell |
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Energy metabolism confined to... |
Mitochondria and chloroplasts |
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Phagocytosis |
Process in which a cell engulfs a food particle and packages it inside a vesicle - enzymes break the particle down and allow it to be processed by mitochrondria |
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Photosynthetic eukaryotes are capable of... |
Interacting with their environment in ways that photosynthetic bacteria cannot - algae can move horizontally, diatoms store nutrients in vacuoles |
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Innovations of dynamic cytoskeleton and membrane systems allowed eukaryotes... |
To obtain the structure required for larger cells with complex shapes and the functional ability to ingest other cells, also evolved complex mechanisms of gene regulation - complex life cycles |
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How do eukaryotes maintain diversity |
Not horizontal gene transfer; sex |
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Animal life cycle |
2n diploid for majority of life cycle, meiosis results in 4 sperm or 1 ovum, 1 sperm from one organism and 1 egg from another form another genetically different from either parent, 2n organism |
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Chloropplasts evolutionary origin |
Chloroplasts ressemble photosynthetic bacteria - cyanobacteria - chloroplasts became permanently incorporated into the eukaryotic cells - endosymbiosis |
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Symbiont |
An organism that lives in closely evolved association with another species |
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Symbiosis |
Association between a symbiont and its host |
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Endosymbiosis |
Symbiosis in which one partner lives within the other |
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Chloroplasts and cyanobacteria linkages |
Structurally similar, biochemistry of photosynthesis found to be essentially the same in cyanobacteria and chloroplasts, chloroplasts have their own DNA and sequences closely match to cyanobacteria |
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But why are some genes missing? |
Some of the chloroplasts' genes were transported to the nucleus when chloroplasts broke or when transferred by a virus |
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Chloroplasts evolved how many times? |
At first, it was thought that they evolved once from a common ancestor of green algae and red algae, but a photosynthetic amoeba has a chloroplast that originated from a branch of cyanobacteria different from the common one |
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Mitochondria |
Endosymbiotic bacteria, live in our cells |
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Hydrogenosomes |
Generate ATP by anaerobic processes, have genes of mitochondrial descent |
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Mitosomes |
Even smaller than hydrogenosomes, but still mitochondrial in descent |
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Hypotheses on eukaryotic cell origin |
1: Eukaryotic cells evolved from an archaeon-like prokaryote and only later incorporated the proteobacterial cell that became a mitochondrion 2: Eukaryotic cells evolved from a symbiosis between an archaeon and a proteobacterium that later became a mitochondrion |
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How do eukaryotes survive in adverse ocean conditions? |
They have hydrogenosomes and support populations of symbiotic bacteria on or within their cells that protect them from the adverse conditions - bacteria gain a free ride maximizing chemoautotrophic growth |
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3 groups with complex multicellularity |
1. Animals 2. Plants 3. Fungi |
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Simple multicellularity |
Filaments, hollow balls, or sheets of little differentiated cells |
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Properties of simple multicellular eukaryotes |
Adhesiveness results in cells sticking together, little communication or transfer of resources, little differentiation between cell types, but still retain a full range of functions like reproduction, every cell in contact with the environment |
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Most simple multicellular organisms are... |
Forms of algae |
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Coenocytic |
Nucleus divides multiple times but the nuclei are not partitioned into individual cells |
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Advantage of simple multicellularity |
Help organisms avoid protozoan predators, help maintain position on water or on a surface (seaweeds) |
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How many times did complex multicellularity evolve? |
6 separate times, in different eukaryotic groups |
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How do certain animals circumvent the limitations of diffusion? |
Sponges - network of pores and canals Jellyfish - interior is not filled with metabolically active cells (mesoglea) Humans - bulk transport |
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Bulk transport |
Means by which molecules move through organisms at rates beyond those possible by diffusion across a concentration gradient - key to complex multicellularity for plants and animals |
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3 requirements for complex multicellularity |
1. Cells must stick together 2. Cells must communicate with one another 3. Cells must take part in a network of genetic interactions that regulate cell division and differentiation (must have gene regulation) |
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Transmembrane molecules that allow for adhesion |
Cadherins, integrins, and more |
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Choanoflagellates |
Closest protistan relatives of animals, unicellular |
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Chonaoflagellate M. brevicollis and cell adhesion |
Choanoflagellate genome contains genes for both cadherin and integrin proteins - stick to substrates |
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Potential original function of adhesion |
Capture bacterial cells, improve predation |
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Choanoflagellates and molecular signaling |
Bacterium - preferred prey of choanoflagellates, when detected choanoflagellates for a novel multicellular structure - facilitate predation |
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Many signaling pathways used for communication first evolved in... |
Single-celled eukaryotes |
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Function of molecular signaling in protistan relatives of complex organisms? |
Signal supplied by food in some cases, nutrients, temperature, or oxygen level, communicate with the same species for sexual reproduction |
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All eukaryotic cells have molecular mechanisms for inter-cellular communication, what makes complex multicellular organisms different? |
Have distinct pathways for communication and the movement of molecules from one cell to another - gap junctions (animals and sponges), plasmodesmata (plants), and channels |
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Why are gap junctions and plasmodesmata necessary? |
Cell wall prevents any entrance into the cell |
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How does growth and cell differentiation occur? |
System of gene regulation, molecular communication between cells - differentiate cells in space rather than time |
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What causes the same gene to be turned on in one cell and off in another? |
Different environments |
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Choanoflagellate, M. brevicollis |
Genome contains genes important in development - signaling with receptor kinases but not as comples - similar with algae and plants |
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Plant cell wall |
Made of cellulose, imparts structured support to cells and mechanical support for plants to stand erect - but plants cannot move |
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Consequences of plants' inability to move |
Development; plant growth is confined to meristems (populations of actively dividing cell at the tips of stems and roots) |
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Animal embryo development |
Fertilized eggs undergo several rounds of mitosis to create a ball of undifferentiated cells (blastula), form a layered structure (gastrula) - brings new cells in contact with one another - new patterns of molecular signaling and tissue specification |
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Oldest complex multicellular fossils |
575 to 555 mya |
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Why did complex multicellularity appear much later than simple multicellularity |
Large, active, and diverse animals can only live in O2 rich environments - O2 levels were low for a long time - only came to present levels 580-560 mya |
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When did complex multicellular land plants evolve? |
Originated about 460 mya |
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Complexities in land plants' evolution from ocean plants |
Must carry out photosynthesis whilst bathed in air and nutrients and water must be absorbed from the soil |
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When did plants with specialized tissues for bulk transport begin to spread across the continents? |
400 mya |
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How did immense diversity among complex multicellular groups arise? |
Functional and ecological reasons - different interactions with surrounding environments, developmental genes |
