STARR Biology EOC What to Expect A total of 54 questions: Cell Structure and Function: 11 questions...

STARR Biology EOC

What to Expect

A total of 54 questions:

• Cell Structure and Function: 11 questions• Genetics: 11 questions• Evolution and Classification: 10 questions• Biological Processes and Systems: 11

questions• Ecology: 11 questions

Cell Structure and Function

• Prokaryotes vs eukaryotes– Both have nucleic acids (DNA and or RNA)– Both have ribosomes– Both have cellular membranes and or cell walls– Eukaryotes have membrane-bound organelles,

prokaryotes do not– Prokaryotes are unicellular, eukaryotes can either be

unicellular or multicellular– Prokaryotes are more primative/simpler than

eukaryotes

Eukaryotic Cell

Prokaryotic Cell

Organelles and their functions:

• Mitochondria: energy and cellular respiration• Ribosomes: protein synthesis (make proteins)• Nucleus: control center, contains chromatin (genetic material)• Endoplasmic reticulum: packaging and sorting proteins• Golgi apparatus: transports proteins• Protein: building blocks of organisms, produced by ribosomes• Cell (plasma) Membrane: barrier that separates inner and

outer cell, maintains homeostasis• Lysosomes: digestion, waste disposal and recycling• Nucleolus: makes ribosomes• Vacuole: storage • Chloroplast: site for photosynthesis in plants

Cellular Processes• ATP (Chemical that stores energy)

• Cellular Respiration:• Two types: Aerobic (with oxygen) and Anaerobic (without oxygen)• Equation for cellular resp. : C6H12O6 + 6O2 --- 6CO2 + 6H2O

• Glycolysis (glucose splitting) first step of respiration that does not require oxygen, only 2 ATP molecules are produced

• Kreb’s Cycle and Electron Transport Chain: breakdown of pyruvic acid, takes place in the mitochondria, can only happen in the presence of oxygen, makes 36 ATP molecules

• Photosynthesis:• Carbon dioxide and water are taken in by plants• Plants absorb light energy and convert it to a usable form.• Energy is used to “fix” carbon dioxide into sugar molecules• Sugar is converted to starch and stored for use by the plant, and by animals

when they eat plants.• Occurs in the chloroplast of a plant cell• Equation: 6CO2 + 6H2O --- C6H12O6 + 6O2

chloroplast

• Endocytosis vs. Exocytosis• Endo: brings substances into the cell; Exo: sends substances

out of the cell

Membrane Transport:• Selectively permeable plasma membrane

Structure ensures …Essential molecules enterMetabolic intermediates remainWaste products exit

• Ways to move across a membrane:• Passive transport does not require an input of energy – down or with

gradient• Passive diffusion - Diffusion of a solute through a membrane without

transport protein• Facilitated diffusion - Diffusion of a solute through a membrane with the

aid of a transport protein• Active transport requires energy – up or against gradient

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(b) Facilitated diffusion—passive transport

(c) Active transport(a) Diffusion—passive transport

ATP

ADP + Pi

Osmosis:• Movement of water across a selectively permeable

membrane• Three types of solutions:

• Hypotonic: there are less dissolved substances such as sugar or salt in the solution than in the cell; water will move into the cell causing it to swell

• Isotonic: there is an equal amount of dissolved substances such as sugar or salt in the solution and in the cell; water will move in and out of the cell at the same rate keeping the cell the same size

• Hypertonic: there are more dissolved substances such as sugar or salt in the solution than in the cell; water will move out of the cell causing it to shrink

• Macromolecules:• Also known as biomolecules, often found in chains called polymers:

• Carbohydrate: biomolecule composed of carbon, hydrogen, and oxygen with a ratio of about two hydrogen atoms and one oxygen atom for every carbon atom.

• Proteins: made up of polymers of amino acids (carbon, hydrogen, oxygen, nitrogen and sometimes sulfer)

• Enzymes are important proteins found in living things. An enzyme is a protein that changes the rate of a chemical reaction.

• Lipids: fats, oils and waxes, made up of carbon, hydrogen and a small amount of oxygen

• Nucleic acids : DNA and RNA, made up of nucleotides (sugar, phosphate and nitrogenous base)

Nucleotide

Water is Polar • A polar molecule is a molecule with an unequal distribution of charge; that

is, each molecule has a positive end and a negative end.

• Water is an example of a polar molecule.• Water can dissolve many ionic compounds, such as salt, and many

other polar molecules, such as sugar.

• Water molecules also attract other water molecules.

• Water resists changes in temperature. Therefore, water requires more heat to increase its temperature than do most other common liquids.

• Water is one of the few substances that expands when it freezes. Ice is less dense than liquid water so it floats as it forms in a body of water

The pH is a measure of how acidic or basic a solution is.

Acids and bases

A scale with values ranging from 0 to 14 is used to measure pH.

More acidic Neutral More basic

Substances with a pH below 7 are acidic. An acid is any substance that forms hydrogen ions (H+) in water.

Substances with a pH above 7 are basic. A base is any substance that forms hydroxide ions (OH-) in water.

Genetics

• DNA carries the instructions for making proteins– DNA vs RNA:

• DNA is double stranded while RNA is single stranded• DNA contains the sugar deoxyribose while RNA has ribose• DNA has the bases Adenine, Thymine, Guanine and

Cytosine while RNA has Adenine, Uracil, Guanine and Cytosine

– DNA and RNA are nucleic acids made up of:• Nucleotides: phosphate group, sugar, nitrogenous base

DNA RNA

Protein Synthesis (making proteins):

– Transcription: occurs in the nucleus when messenger RNA (mRNA) makes a copy of the DNA

– Translation: occurs at a ribosome where mRNA lines up as transfer RNA (tRNA) delivers the appropriate amino acids to the mRNA sequence

Nucleus

Ribosome

The study of heredity started with the work of Gregor Mendel and his pea plant gardenMendel was an Austrian Monk that lived

in the mid 1800’s

Genetics: The study of heredity, how traits are passed from parent to offspring

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Punnett SquareUsed to help solve genetics problems

Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity Monohybrid cross - cross involving a single traite.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height

Alleles – alternate or two different forms of a gene (dominant & recessive) Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R) Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r) Genotype - gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white)

Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR: homozygous dominant or rr: homozygous recessive); also called pure

Heterozygous genotype - gene combination of one dominant & one recessive allele (e.g. Rr); also called hybrid

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Mendel’s Laws

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Law of Dominance

In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.

All the offspring will be heterozygous and express only the dominant trait.

RR x rr yields all Rr (round seeds)

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Law of Dominance

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Law of Segregation

• During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.

• Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

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Applying the Law of Segregation

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Law of Independent Assortment

• Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

• This law can be illustrated using dihybrid crosses.

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Let’s Solve Together

• In guinea pigs, the allele for short hair (S) is dominant to long hair (s), and the allele for black hair (B) is dominant over the allele for brown hair (b). What is the probable offspring phenotype ratio for a cross involving two parents that are heterozygotes for both traits?

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Dihybrid Cross• Short hair = dominant = SS or Ss Long

Hair = recessive = ss Black coat = dominant = BB or Bb Brown coat = recessive = bb

• SsBb x SsBb (gametes done by the FOIL method)–SB, Sb, sB, sb and SB, Sb, sB, sb

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SB Sb sB sb

SB SSBB SSBb SsBB SsBb

Sb SSBb SSbb SsBb Ssbb

sB SsBB SsBb ssBB ssBb

sb SsBb Ssbb ssBb ssbb

SsBb x SsBb

The Cell Cycle:

• Mitosis • Meiosis

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30

Cell cycle

• G1 – first gap• S – synthesis of DNA Interphase• G2 – second gap• M – mitosis and cytokinesis

• G0 – substitute for G1 for cells postponing division or never dividing again

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Two daughter cells form, eachcontaining 6 chromosomes.

S

M G2G1

Interphase

Cytokinesis

Telo

phas

eAn

apha

se Metaphase

Prometaphase

Prophase

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34

Meiosis

Sexual reproduction requires a fertilization event in which two haploid gametes unite to create a diploid cell called a zygote

Meiosis is the process by which haploid cells are produced from a cell that was originally diploid


Meiosis I

Meiosis II

Sister chromatids

4 haploid cells with individual chromosomes

G1 phase prior to meiosis

Homologous pairof chromosomesprior tochromosomalreplication

A diploid cell

Diploid cellwith replicatedand condensedchromosomes

Haploid cellswith pairsof sisterchromatids

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(c) Metaphase I(b) Prometaphase I

CentrosomeSpindle forming

Bivalent

Bivalent

Meiosis I

Meiosis II

(a) Prophase I

(g) Prometaphase II(f) Prophase II (h) Metaphase II

Metaphaseplate

Sisterchromatids

(e) Telophase I and cytokinesis(d) Anaphase I

(i) Anaphase II

Cleavage furrow

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(e) Telophase I and cytokinesis(d) Anaphase I

(i) Anaphase II (j) Telophase II and cytokinesis

Four haploid cells

Cleavage furrow


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Meiosis vs. Mitosis

Mitosis produces two diploid daughter cells that are genetically identical6 chromosomes in 3 homologous pairs

Meiosis produces four haploid daughter cellsEach daughter has a random mix of 3

chromosomes

Evolution and Classification:

Theory of Evolution:

Mechanism for change in a population; occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation.

Natural Selection

Gradual change in a species through adaptations over time.

Evolution and Classification:

HMS Beagle Voyage 1835

Darwin studied the changes in the beaks of Finches

Darwin’s key ideas:

• A. REPRODUCTION: Organisms produce more offspring than can survive

• B. VARIATION:Variety in traits exist• C. SURVIVAL OF THE FIT: Some traits allow

survival & are passed on• D. Over time certain variations make up most

of a population & they may be different from their ancestors

Evolution Evidence:

1. Adaptations2. Fossils3. Comparative anatomy4. Comparative embryology5. Comparative Biochemistry6. Plate Tectonics

Comparative Anatomy Structures:Analogous:1. Different ancestors2. “analogy”=like3. Different underlying

structures4. Same Function5. Similar Environments

Homologous:1. Same ancestor2. “homo”=same3. Same underlying

structures4. Different

Functions5. Different

Environments

Analogous Structures• Different underlying structures (different

ancestors)• Same function, similar environments

Fly wing

Bird Wing

Homologous Structures: Same underlying structures, different functions, different

environments & common ancestor

Vestigial Structures- structures in a present-day organism that no longer serve its natural purpose, but was probably useful to an ancestor,

provides evidence for evolution

4. Comparative embryology:

Similar embryo development in closely related species

Camouflage-enables a species to blend with their surroundings to avoid detection by predators

Mimicry-enables one species to resemble another species; may provide protection from predators or other advantages

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Taxonomy

• Hierarchical system involving successive levels• Each group at any level is called a taxon• Domain

– Highest level– All of life belongs to one of 3 domains– Bacteria, Archaea, and Eukarya

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Eukarya

lupus

Canis

Canidae

Carnivora

Mammalia

Chordata

Animalia

Domain

Species

Genus

Family

Order

Class

Phylum

Kingdom

~270

1

7

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~5,000

~50,000

>1 million

OpisthokontaSupergroup >1 million

Taxonomicgroup

Gray wolffound in

Number ofspecies

~ 4– 10 million

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Binomial nomenclature

• Genus name and species epithet• Genus name always capitalized• Species epithet never capitalized• Both names either italicized or underlined• Rules for naming established and regulated by

international associations

• Example: Homo sapiens

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Phylogenetic trees

• Phylogeny – evolutionary history of a species or group of species

• To propose a phylogeny, biologists use the tools of systematics

• Trees are usually based on morphological or genetic data

• Diagram that describes phylogeny• A hypothesis of evolutionary relationships

among various species

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Present

5

10

A

B

B

CD

E

F G HI J K

Mill

ions

of y

ears

ago

(mya

)

Tim

e

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(b) Cladogram based on morphological traits

Lamprey Salmon Lizard Rabbit

(a) Characteristics among species

Notochord Yes Yes Yes Yes YesNo Yes Yes Yes YesNo No Yes Yes YesNo No No Yes YesNo No No No

VertebraeHinged jawTetrapod

Lancelet Lamprey Salmon Lizard Rabbit

YesMammaryglands

Vertebrae

Hinged jaw

Tetrapod

Lancelet

Notochord

Mammaryglands

Cladograms:

• Ecology is the study of interactions that take place between organisms and their environment.

• All the living organisms that inhabit an environment are called biotic factors.

• The nonliving parts of an organism’s environment are the abiotic factors. Examples of abiotic factors include air currents, temperature, moisture, light, and soil.

• Ecosystem: Populations of plants and animals that interact with each other in a given area and with the abiotic components of that area.

• A niche is the role or position a species has in its environment—how it meets its specific needs for food and shelter, how and where it survives, and where it reproduces in its environment.

Ecology:

Symbiosis• Symbiosis: means “living together”; there are 3 types of

symbiotic relationships• Parasitism: the host is harmed and the parasite benefits (ex: human and

a tapeworm)

• Commensalism: one organism is not harmed nor benefited and the other organism benefits (ex: tree and a bird)

• Mutualism: both organisms benefit (ex: termite and paramecium)

Host Parasite

- +

Organism Unaffected Organism Benefited

0 +

Organism Benefited Organism Benefited

+ +

Food Chains• Food Chain: represents the flow of energy in an ecosystem; the arrows represent

the direction of energy flow and are called trophic levels, there are usually 3-4 trophic levels in a food chain, but no more than 5 levels

Grass Insect Bird Hawk (plant) (herbivore) (carnivore) (carnivore)

• Producer: organisms that undergo photosynthesis (grass); these are also called autotrophs

• Consumer: organisms that must eat producers/consumers; these are also called Heterotrophs

• Primary consumer: these organisms eat the producers (insect)

• Secondary consumer: these organisms eat the primary consumers (bird)

• Tertiary consumer: these organisms eat the secondary consumers (hawk)

PyramidsThere must always be more prey than predators because the predators can

not use all the energy that is consumed from the prey. The lower an organism is on the food chain, the higher the numbers of these organisms. The more organisms there are at a trophic level, the more mass the group

of organisms has.

Energy Pyramid Number Pyramid Biomass Pyramid

Grasses100%

Grasshoppers10%

Birds 1%

Fox0.1% Birds

10 kg

Fox1 kg

Grasshoppers100 kg

Grasses1000 kg

STARR Biology EOC What to Expect A total of 54 questions: Cell Structure and Function: 11 questions...

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Transcript of STARR Biology EOC What to Expect A total of 54 questions: Cell Structure and Function: 11 questions...