Biology final

1/15/24 

Science: 

• A collection of information about the natural world 

• A process of discovery that helps us to understand the natural world 

• Measurements and comparison 

“Rules” of science: 

• Attempts to explain the natural world 

• Evidence, must be testable 

• Does not make moral/aesthetic judgements 

Scientific Method 

• No “real” order 

• Exploration and discovery 

• Testing Ideas 

• Community analysis and feedback 

• Benefits and outcomes 

• Complex/unpredictable 

Vocab: 

• What you can see or measure  

• Observations, facts, evidence, data 

• An attempt to explain or predict what you can see 

• Ideas 

Hypothesis: proposed explanations, narrow set of observations 

• Theories:  powerful explanations, wide set of observations, strongly supported 

• Overarching theories: frame entire disciplines, broadly supported by many lines of evidence 

• Hypothesis cannot become a theory, and theories cannot become laws 

• Scientific Laws: an observation, not an explanation  

• Science accepts ideas, but does not prove them 

LIFE:  

• Atoms 

• Carbon based lifeforms (friendly- lots of space to make bonds) 

• Molecules 

• Unique properties of life emerge as certain kinds of molecules become organized (into cells) 

• Monomers: single chain 

• Polymers: multiple 

• Lipids: hydrophobic 

• Composition –> structure -> function 

Reductionism: taking a system apart to its parts 

Complex Systems Theory: whole> sum of parts 

Emergence: behaviors/patterns emerging from  complex systems made up of many individuals components interacting in complex ways 

• Bottom up 

• Each step upwards in the levels of complexity, new properties emerge that were not present at simpler level (bc of interactions, collective behavior) 

Cells: smallest unit of life 

1^st  law thermodynamics: energy cannot be created or destroyed, but can trasform 

2^nd law: as more heat is lost to surroundings – increase randomness 

• Entropy: measure of how much energy in a system is dispersed 

To maintain organization/complexity:  

• Requires: energy flows and nutrients cycles 

• Energy (the ability to do work) 

• Holds parts together 

• Nutrients (elements) 

• The parts 

• Producer: autotrophs 

• Consumers: heterotrophs 

Metabolism: all chemical reactions required to keep you alive 

Homeostasis: internal conditions balanced, favor cell survival/metabolism 

Gene: segments of DNA molecules that store information 

• In a particular place on a chromosome, indirectly determines traits 

• Recipe/blueprint (molecules) for making our proteins ------ protiens control our traits 

Gene expression = protein synthesis: the sequence of a gene determines the amino acid sequence of a protein 

Transcription: copying the gene  

• DNA ---- RNA 

Translation: building the protein  

• RNA ---- Protein 

Types of RNA: 

MRNA: 

RRNA 

TRNA: carries amino acids 

Proteins: structure and function  

• Function: enzymes (help chemical reactions) 

Chromosome:  

• General definition: a DNA molecule or “hereditary units” 

• Specifics definition:  

• Tightly packaged DNA 

• Only found in cell division 

• Cannot be used by cell to produce proteins 

Homologous Chromosomes: not identical, one from dad one from mom, but same genes at same location, may have different alleles 

Homozygous: alleles at a specific locus are identical in a pair of chromosomes 

Ex: GG or gg 

Heterozygous: Gg 

Dominant Allele: Allele will be expressed when at least one copy is present 

Recessive: only expressed if two copies are present 

Hereditary information is contained in genes (made of DNA) located on chromosomes. 

Alleles: alternate forms of a single gene and are found at the same locus on homologous chromosomes. 

MENDELS SEGREGATION: 

• Pairs of alleles separate during the formation of gametes (meiosis) 

• Each gamete has one allele form each pair 

• Fertilization gives each offspring two new alleles 

INDEPENDENT ASSORTMENT: 

• Which way the chromosomes line up is random 

• Pairs of alleles  

Chromatin: 

• A state of organization of chromosomes 

• Unwound 

• Uses DNA 

• Can be used by the cell to produce proteins 

Histone: types of organizational/structural proteins found in chromosomes 

Nucleosome: the unit that includes the DNA wrapped around the histones 

DNA replication:  duplicates single strand of chromatin to X 

Human genome has : 23 pairs and 2 sets of 23 

Haploid: 1 set of chromosomes 

Diploid: 2 sets of chromosomes 

Homologous pair of chromosomes: identical? No 

• X X – pair of sister chromatids , one from each parent  

Mitosis: 

• Why: injury repair, growth, replacement  

Duplicatede chromosomes line up in middle 

sister chromatids separate 

Results in two identical cells 

Does not change the number of chromosomes 

Meiosis: 

• Why? Makes gametes – haploid  (sperm and egg) 

• Zygote= first cell of next generation 

• Fertilization 

• Duplicated chromosomes line up in pairs 

Meiosis 1 

• Line up and Homologous chromosomes separate 

Meiosis 2 

• Sister chromatids separate 

RESULT: four different cells, produces haploid cells that are all unique 

Fertilization> formation of zygote  

Locus: location of a gene on a chromosome  

Phenotype: physical appearance  

Genotype: genetic makeup 

Linkage: traits carried on the same chromosome cannot assort independently 
- resulting in fewer possible combinations in the haploid cells  

Alleles on the same chromosome experience linkage, but if crossing over occurs then they can sort independently 

Genes, indirectly through the proteins, control dominance and recessive 

Gene codes for an enzyme: controls the trait 

Systematic Biology: 

Taxonomy: name, discover, describe, classify life 

• Domain is most general, species most specific 

Phylogeny: a hypothesis of evolutionary relationships 

• Phylogenetic tree: a hypothesis based on a given set of data 

• Graph of evolutionary relationships  

• And explanation of the observed patterns of similarities and differences. 

• Node: hypothetical common ancestor 

• Most important part: has information 

Viruses: “alive” not yes or no 

• Not cellular,  

• not move on their own,  

• no metabolism or homeostasis 

• No reproduce on their own 

• Biomolecules 

• Have genetic info 

• Genetic code same as living things 

• Evolve 

Definition: parasitic biochemicals 

• genetic material with protein coat (capsid) 

• Protective envelop derived from host cell membrane 

• “Viron” - completed virus particle 

• How do they work? 

• Viral replication: attach and enter a host cell to reproduce 

• 1. attaches to host cell (proteins) 

• 2. genetic material or virus enters cell 

• 3.   

• 4. virus particles are assembled 

• 5. new virus particles are released from infected cells to attack other host cells  

Viruses cause disease by killing host cell or causing it to malfunction 

• The nature of the disease depends on which cells are infected 

Prokaryotes: 

• No nucleus 

• No membrane bound organelles 

• Circular chromosomes 

Eukaryotes: 

• With nucleus 

• Membrane bound 

• Linear chromosomes 

• 10-100xlarger 

• became multicellular  

• Sexual reproduction = meiosis + fertilization 

Domains: 

• Bacteria (most diverse, individuals, species) 

• Archaea (extreme environments) 

• Eukarya: animals, fungi, plants, protists (they have their own lineage, anything but animals, fungi, plants) 

• LAND PLANTS: cellulose cell walls 

• Alternation of generations lifecycle  

• FUGAL DIVERSITY: 

• Every cell is on the surface of its body 

• Filamentous (a few single-celled) 

• Eukaryotic 

• Haploid dominant 

• ANIMALS: 

• Diploid dominant 

• Humans are chordates 

Endosymbiotic Theory 

Three major kinds of sexual lifecycles: 

1. Diploid dominant 

2. Haploid dominant 

3. Alternation of generations 

1. All follow a basic pattern (meiosis and fertilization) 

1. Haploid (1N) 

1. Sex 

2. Diploid (2N) 

Fungi: zygote does not grow, goes to meiosis and mitosis  

• Spores germinate and grow  

• Adults in fungi are haploid 

• Theres only 1 set of chromosomes in all those cells 

True or false 

Zygotes growt to produce a multicellular adult? Sometimes, fungi don't grow 

Animals have a haploid dominant lifecycle:  false 

Plant sporophytes are haloid: false 

Spores are haploid: true 

Meiosis produces gametes: sometimes , true in animals false in plants/fungi 

Diploid dominant: the multicellular stage is on the diploid side ‘ 

Haploid dominant: the multicellular stage is on the haploid side.  

Zygote doesn't “grow” 

Alternation of generations: multicellurlar both sides of the lifecycle ex: ferns 

EVOLUTION:  

descent with modification 

Inheritance of acquired characteristics 

Homology: similarities are inherited from a common ancestor 

Analogy: adaptations from having a similar environment  

Bones in a bird vs bat EXAMPLE 

Wings are analogous but their bones are homologous 

EVOLUTION: a change in the gene pool from one genration to the next 

Gene pool:  the genetic makeup of a population 

 The process of evolution : 

REQUIREMENTS: 

Level of biological organization: population 

Need variation of a heritable trait in a gene pool 

MECHANISMS: 

1. Mutations: must be heritable 

2. Gene flow: migration 

1. Exchange of genes between populations 

2. Gene movement from another population 

3. Can introduce new alleles 

4. Reduces variation btw populations 

5. Increases variation in within populations 

6. Slows, or prevents speciation 

3. Nonrandom mating 

4. Genetic drift: random change in allele frequencies 

1. Increase variations btw populations 

2. Decrease variation within population 

5. Selection 

1. Survival related to phenotype or genotype 

In class questions: mechanisms 

Which result in adaptation: selection 

Which adds new alleles to a population: gene flow and mutation 

Which will decrease varation within a population: nonrandom mating, genetic drift, selection 

Which will decrease variation between populations: gene flow  

Which will increase variation between populations: Mutations, nonrandom mating, genetic drift, selection 

ADAPTATION is not EVOLUTION 

Adaptation is a result of evolution by natural selection 

Adaptation: a useful trait increasing in the pop 

Noun: a favored trait that increases frequency 

Verb: an increase in the frequency of a favored trait 

Evolution: changing the gene pool from one gen to the next 

Natural selection: mechanism that causes gene pool to change 

- it can also prevent change  

Types of Natural Selection:  

• Stabilizing selection: selection against the extremes 

• Loss of variation 

• Increased adaptation to a constant environment 

• Directional selection: selection against only one extreme 

• Adaption to a changing environment  

• Disruptive selection: either extreme is favored over intermediate 

• Separation of population into 2 distinct groups 

More results of Evolution: 

• Microevolution: “short term” 

• Changes in the gene pool from one generation to the next 

• Macroevolution” “Long term” 

• Speciation: the formation of a new species  

Species: Not a level of biological organization 

• Not really definable  

• It's a taxonomic classification:  

• It's the most specific, domain is the most general 

Definition: “type” of living thing based on characteristics 

Speciation: a splitting event that produces two species 

• An accumulation of genetic differences between populations over time  

• Eventually results to the inability to interbreed 

Reproductive isolation: lack of gene flow between populations 

• Promotes speciation 

• The opposite of “gene flow” 

1. Prezygotic Isolating Mechanisms 

1. Prevent successful formation of zygote (before egg fuses with the sperm) 

• geographic isolation 

• Habitat isolation 

• Temporaral isolation (time) 

• Behavioral isolation 

Mating attempt: 

• Mechanical isolation 

• Gamete isolation 

2. Postzygotic isolating mechanisms 

1. Prevent hybrid offspring from being successful (after egg fuses with the sperm) 

• Hybrid mortality 

• Reduced hybrid viability 

• Reduced hybrid fertility and hybrid breakdown