KEYSTONE REVIEW 2CELL CYCLE THROUGH ECOLOGY

CELL CYCLEThere are two different types of cell reproduction, based on WHICH type of cells are being reproduced-Body cells, or somatic cells, undergo MITOSIS-Sex cells, or gametes, undergo MEIOSIS-Prokaryotic cells, like bacteria, undergo a different process called binary fission

-binary fission is the splitting of the entire cell into two new cells.

CELL CYCLEChromosome structure. How many chromosomes do humans in each cell?

Centromere

Chromatid

CELL CYCLEBoth mitosis and meiosis consist of several phases:1. Interphase2. Prophase3. Metaphase4. Anaphase5. Telophase6. Cytokinesis

CELL CYCLEInterphase1. Interphase has three stages

1. G1: first growth phase. In G1 the cell grows bigger so that it does not get smaller and smaller with each reproduction

2. S: synthesis phase. In S phase, the cell replicates it’s DNA (DNA replication!). The cell does this so that each time it reproduces, it does not lose half of it’s DNA to the new cell. If the cell DID lose half it’s DNA to the new cell, eventually there would be no DNA left in new cells that are being produced.

3. G2: second growth phase. In G2 the cell grows more and prepares for EITHER mitosis or meiosis (depending on the type of cell, right?!)

CELL CYCLEMitosis1. Interphase (previously covered)2. prophase: in this phase the cell’s nuclear membrane

starts to dissolve and the chromosomes are free-floating in the cell. The chromosomes begin to uncoil so that they are easier to move around. Spindle fibers begin to form. They are responsible for moving chromosomes around.

3. Metaphase: in this phase, the chromosomes line up on the equator of the cell.

CELL CYCLE4. Anaphase: in this phase, the chromosomes are being

pulled to opposite poles of the cell by the spindle fibers. Spindle fibers attach to the chromosome at the centromere. The chromosomes are split into smaller segments, but are still referred to as chromosomes!

5. Telophase: in the phase, the cell’s cytoplasm beings to separate into two cells

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

CELL CYCLEMitosis-Cytokinesis: occurs after telophase, but it technically not a “phase” of mitosis or meiosis. During cytokinesis, the cytoplasm of the cell divides, producing two cells

CELL CYCLEMeiosis-Meiosis goes through the cell cycle twice. Why? Because gametes need only half of the amount of chromosomes as somatic cells do. This is because two gametes must join together (sperm + egg) to produce a zygote, or fertilized egg. If gametes had a full set of chromosomes, sperm + egg= double the amount of chromosomes needed. More than the required amount of chromosomes results in genetic disorders/ even death of the cell.

CELL CYCLEMeiosis 11. Interphase (previously covered)2. Prophase 1: nuclear membrane dissolves, chromosomes

uncoil.3. Metaphase 1: chromosomes line up on the cell’s equator

with their homologous pair

CELL CYCLEMeiosis4. Anaphase 1: Homologous chromosomes separate to either pole of the cell. They are pulled by spindle fibers attached to their centromeres.5. Telophase 1: The cell prepares for cytokinesis

CELL CYCLEMeiosisThe cell does NOT go through interphase twice. Why? Because during interphase, the cell replicates it’s DNA (during S phase), and this would result in again, a doubled amount of chromosomes for a gamete cell.

CELL CYCLEMeiosis 21. Prophase 2: cell’s nuclear membrane dissolves,

chromosomes uncoil2. Metaphase 2: chromosomes line up on the equator of the

cell, pulled there by spindle fibers3. Anaphase 2: spindle fibers, attached to the

chromosome’s centromere, pull the chromosomes to opposite poles of the cell. The chromosomes are now smaller segments, but still referred to as chromosomes!

4. Telophase 2: the cell prepares for cytokinesis

Prophase 1

Metaphase 1-homologs line up

Anaphase 1

Telophase 1

Cytokinesis

Prophase 2

Metaphase 2

Anaphase 2

Telophase 2

Cytokinesis

GENETICSAllele: a form of a gene such as B or b. Every person has (at least) two for each geneGene: a segment of a chromosome that codes for a specific trait, such as hair colorGenotype: the alleles you have for a certain trait

ex: BB, Bb, bbPhenotype: the physical trait that you have (because of the alleles you have

ex: brown hair, blonde hair

GENETICSMendel: a monk who first studied genetics using pea plants from his garden. He discovered dominant/recessive traits.

P p

P PP Pp

p Pp pp

P and p are the two alleles for the character of flower color.

PP is one combination which = purple flowersPp is combination which = purple flowerspp is one combination which = white flowers

There are only TWO traits, purple or white

F1EGGS

F1 SPERM

GENETICSDominant: the form of the character that is expressed physically. It is represented by a capital letter, such as BRecessive: the form of the character that is not expressed physically, unless there are two recessive alleles. It is represented by a lower case letter, such as bHeterozygous: two alleles that are different, one dominant and one recessive, BbHomozygous: two alleles that are the same

-homozygous dominant: two dominant, BB-homozygous recessive: two recessive, bb

GENETICSPunnett square: a tool used to determine the possible genotypes and phenotypes of offspring between two parentsMonohybrid cross: examines ONE trait at a time

GENETICSDihybrid cross: examines two traits at a time.*special technique for setting up the punnett square

FOILParent= GgYy

Possible gametes: GY, Gy, gY, gy

GENETICSComplex patterns of heredity: traits that don’t follow Mendel’s rules of dominant/recessive.

-sex-linked: traits that are carried on the X or Y chromosomes

-multiple alleles: traits that are controlled by more than two alleles

-incomplete dominance: traits that don’t show just dominant/recessive phenotypes

-codominance: traits that don’t have a recessive alleles or phenotype

GENETICSIncomplete dominance: the dominant gene is not “dominant” enough to completely mask the recessive gene in a heterozygous genotype. Ex: flower color in snapdragon flowers

GENETICSCodominance: there is no recessive gene. There are two genes that are equally dominant. We cannot use our normal capital/lower case lettering system.Instead we use superscripts: IGIG and IBIB

GENETICSMultiple alleles: there are more than two alleles that control a trait. There are still dominant and recessive genes, but since there might be more than one, we use superscripts.

GENETICS

GENETICSSex-linked: the genes for these traits are found on the X or Y chromosomes

XX=femaleXY=male

GENETICSPolygenetic inheritance: when more than one gene controls a trait (not just more than one allele, that’s called multiple alleles). Results in many variations, not just two (one dominant, one recessive).

ex: Skin color, hair color, eye colorEpigenetics: traits that are influenced by the environment

ex:

Hydrangea: same genotype for flower color express different phenotypes depending on the acidity of the soil

Artic fox: fur color is affected by temperature. During the summer, the fox produces enzymes that makes pigments. These pigments darken the fox’s coat to a reddish brown so the fox can blend in with the summer landscape

Human height: influenced by nutrition.Human skin: influenced by exposure to sun

GENETICSPedigree: a tool used to determine how traits are passed down through generations

EVOLUTIONHow did life form on Earth?

The Bubble Model

1. gases (from underneath the Earth’s crust) were trapped in underwater bubbles2. gases underwent chemical reactions3. gases were ejected into the atmosphere4. gases underwent further reactions5. simple and complex compounds fell into the oceans, such as carbon, oxygen, and nitrogen6. These molecules formed RNA, which made the first proteins7. Proteins are the building blocks of all living things

EVOLUTIONEndosymbiosis: how eukaryotes were formed from prokaryotes

EVOLUTIONThe move to dry land-Life on Earth was unsafe due to the extreme heat and ultraviolet radiation from the sun-Ozone was formed and served as a protective barrier from ultraviolet radiation

-ozone formed when oxygen, released by prokaryotes performing photosynthesis underwater, reacted with sunlight (O3).

EVOLUTIONOther ways the Earth has changed:

-Continental drift: the continents sit on plates that can shift/move. The continents were once all connected and created a large land mass known as Pangaea.

-Species have evolved

EVOLUTIONHow have species evolved?Darwin was the first to study and develop theories about how evolution was occurring in plant and animals. He studied finches on the Galapagos Islands.

EVOLUTIONSpecies: a group of similar organisms that can interbreed successfully, and produce successful offspring

ex: humans. nonex: donkeys (horse + mule). They are sterile

Population: a species living in a particular areaex: humans in pennsylvania

EVOLUTIONNatural selection: the environment “chooses” which individuals survive based on which traits they possess

ex: brown deer are naturally selected FOR because they are able to blend in with their environment and avoid predators. White deer are naturally selected AGAINST because they stick out in their environment.

Do traits disappear?

EVOLUTIONAdaptation: when a particular trait is selected for over time, because it is advantageous, and therefore becomes more common in the population

Ex: peppered moths (lab from class)

EVOLUTIONFitness: the measure of how successful a particular organism is. We say its measured in “grandchildren”. The more offspring you produce, the more fit you are because you are surviving long enough to reproduce

ex: a cod laying 1 million eggs (all survive, for example), is more fit than a panda who only has one cub.

EVOLUTIONTypes of natural selection1. Disruptive: natural

selection shifts so that two traits are favored

2. Stabilizing: natural selection shifts slightly so that the average trait is again favored

3. Directional: natural selection shifts in one direction, in favor of one trait

EVOLUTIONSpeciation: the formation of a species. Two types of speciation are convergence and divergence. -Divergence: the accumulation of differences among organisms that share a common ancestor-Convergence: the accumulation of differences among organisms that come from different lineages

EVOLUTIONHow does speciation occur? 3 ways1. Reproductive isolation: a species begins to diverge because of

mate preferences. They choose to stop breeding as a whole and evolution occurs in the two different groups.1. Ex: flies and starch/sugar food preference

2. Geographical isolation: a species begins to diverge because they are physically separated and can no longer breed. The two groups evolve separately.1. Ex: pup fish in death valley

3. Behavioral isolation: a species begins to diverge because they have different behaviors and they choose to stop breeding as a whole. Evolution occurs separately in the two groups.1. Ex: blue footed boobie bird mating dances

EVOLUTIONRESULTS of the 3 types of speciation1. Sympatric speciation: when two new species diverge

because of reproductive or behavioral differences. They are from the same homeland, but chose not to breed.

2. Allopatric speciation: when two new species diverge because of geographic differences. They are from different homelands and can therefore not breed

EVOLUTIONTypes of evidence:1. Molecular/DNA evidence: similar DNA means there is a

shared ancestor2. Comparative anatomy: similar bone structures/physical

attributes means there is a shared ancestor3. Embryology: similar embryo and fetus

structure/appearance means there is a shared ancestor4. Fossils: similar ancient organisms means that organisms

that evolved over time, or that we came from those organisms.

EVOLUTION

TAXONOMYTaxonomy is the classification of living things.Classification system: domain, kingdom, phylum, class, order, family, genus species. Genus and species make up an organism’s scientific name

ex: Panthera pardus

TAXONOMY

TAXONOMYWe can determine when certain traits evolved over time, as well as which organisms are more closely related by studying cladistics and phylogeny.

TAXONOMY

TAXONOMYA dichotomous key: a tool used to determine unknown species

ECOLOGYPopulation: a species living in a particular area

-How does population size change? Births, deaths, immigration and emigration

-How are species spread out in their habitat? Pattern of dispersion

1. Clumped2. Random3. Uniform

ECOLOGYCarrying capacity: the amount of individuals that an environment can support.-Things that influence carrying capacity

density-dependent factors: affect the population differently, depending on its size

ex: food, space and predationdensity-independent factors: affect the population in the same way, no matter how large or smallex: natural disasters and weather

ECOLOGYTypes of populations: K-selected: organisms that have a long life span, but produce few offspring

ex: humans, pandas, elephants and large plantsr-selected: organisms that have a short life span, but produce many offspring

ex: rodents, pests and weeds

Characteristics r-selected K-selectedMaturation time Short Long

Lifespan Short Long

Death rate Often high Usually low

#offspring/episode Many Few

# reproductions/lifetime

Usually one Often several

Timing 1st reproduction

Early in life Late in life

Size of offspring/eggs Small Large

Parental care none Often extensive

ECOLOGYHow populations evolve1. Mutations: changes in DNA resulting in unique

individuals (GOOD)2. Natural selection: traits (and individuals) are selected for

(GOOD)3. Genetic drift: a natural disaster affects a population,

causing a loss in genetic differences (BAD)4. Gene flow: genes/traits being transferred throughout

several populations, increases diversity (GOOD)5. Nonrandom mating: organisms choosing their mates

based on physical appearance, reduces diversity (BAD)

ECOLOGYHardy-Weinberg: two scientists that studied populations-Came up with the model for an ideal population (couldn’t exist in real life)-Came up with the forces that affect populations (previous slide)-Came up with a formula for determining allele frequencies in a population

ECOLOGYp=frequency of one allele (A) q=frequency of the other allele (a)

• p+q=1.0 • (p=1-q & q=1-p)

P2=frequency of AA genotype2pq=frequency of Aa plus aA genotype; q2=frequency of aa genotype;

• p2 + 2pq + q2 = 1.0

ECOLOGYCommunity: many species living together and interactingTypes of interactions1. Coevolution: when two species are evolving at the same

time. EX: bees and flowers, fox and rabbits2. Predation: killing another organism for food (+/-). EX: fox

kills rabbit3. Parasitism: when a parasite uses a host for food (+/-). EX:

tick on dog4. Mutualism: when two species depend on one another (+/+).

EX: clown fish and anemone5. Commensalism: when one species benefits and the other is

not harmed/helped (+/0). EX: barnacles on a whale

ECOLOGYCompetition: when two, or more, species compete for resources within the same environment. Results in a realized niche.

ex: competing over food, water, shelter and spaceNiche: an organisms role in an environment

-fundamental niche: all the resources an organism WANTS to have

-realized niche: all the resources an organism CAN have because there is competition

ECOLOGY

ECOLOGYBiome: a major biological community that occurs over a large area of land

• Aquatic• Freshwater regions (ponds and lakes, streams and rivers and

wetlands), marine regions (oceans, coral reefs, and estuaries)• Desert

• Hot and dry, semiarid, coastal, cold• Forests

• Tropical, temperate, and boreal (a.k.a taiga)• Grasslands

• Savanna and temperate grassland• Tundra

• Artic and alpine

ECOLOGYEcosystem: all of the living and nonliving things interaction in an environment-abiotic factors: nonliving things such as rocks, weather, soil, and water-biotic factors: living things such as plants and animals

ECOLOGYChange of ecosystems over time

• Succession: the regular progression of species replacement • Primary succession: succession that occurs where life has not

existed before• Volcanic areas and once-glacier covered areas

• Secondary succession: succession that occurs in areas where there has been previous growth

• Abandoned fields or forest-clearings

ECOLOGYMovement of energy through ecosystems

• Primary energy source is the sun• Producers: organisms that first capture energy

(photosynthesis)• Ex: plants

• Consumers: organisms that consume plants or other organisms to obtain energy

ECOLOGYTypes of consumers:- Carnivores: eat meat

- Ex: wolf- Herbivores: eat plants

- Ex: deer- Omnivores: eat both plants and meat

- Ex: bears- Detritovores: break down dead matter for food

- Ex: worms

ECOLOGYTrophic levels: energy levels within an ecosystem. Energy is transferred from one level to the next, but some energy is lost along the way in the form of heat.

ECOLOGYFood web: shows “who eats who” and how energy is transferred in an ecosystem

ECOLOGYBiogeochemical cycles

• Occur when a substance enters living organisms, such as trees, from the atmosphere, water or soil

• Water cycle, carbon cycle, and the phosphorous and nitrogen cycle

ECOLOGYThe environment is affected by1. Acid rain:

• sulfur, introduced to the atmosphere by smokestacks, combines with water vapor to produce sulfuric acid. Rain and snow carry the sulfuric acid back to the earth’s surface

2. The greenhouse effect:• The earth would be as cold as the Moon except for the insulating effects of

certain gases-called greenhouse gases-such as water vapor, carbon dioxide, methane, and nitrous oxide in the atmosphere

• Chemical bonds in carbon dioxide molecules absorb solar energy as heat radiates from the Earth

• This process-called the greenhouse effect-traps heat within the atmosphere 3. Destruction of the ozone layer:Remember, the ozone protects the Earth from the ultraviolet rays of the sun

• There is a hole in the ozone due to chlorofluorocarbons (CFCs)• Used as coolants in refrigerators, air conditioners• Used as aerosol propellants in spray cans• Used in foaming agents in the production of plastic-foam cups and

containers