BIOLOGY 138

Semester 2 Study Guide

Created by James Feng, based off of Charles Feng

I. Meiosis

Meiosis

- all 4 daughter cells have 1/2 as many

chromosomes

- divides twice

- haploid result

Mitosis

- the 2 daughter cells have the same

amount of chromosomes

- divides once

- diploid result that is identical to parent

Meiosis produces haploid gametes in diploid organisms. Why is this important?

Producing haploid gametes keeps the chromosome number from doubling every

generation.

Meiosis

A haploid sperm cell fuses with a haploid egg cell in the process of fertilization. This

creates a fertilized called a zygote, which is diploid.

Fertilization

A karyotype is a display of chromosomes in an orderly array. Karyotype

Homologous chromosomes are a pair of the same type of chromosomes. They have the

same length, same genes, and same position of the centromere. However, they are able

to carry different versions of the same gene, like blue eyes versus brown eyes (alleles!).

Homologous

Chromosomes

If something is haploid, it only has 1 set of chromosomes.

These include gametes, or sex cells (egg+sperm).

Haploid (1n)

Diploid (2n) If a cell is diploid, it has two complete sets of chromosomes, one set from each parent.

These include somatic (body) cells.

Stages of Meiosis

Meiosis I:

Anaphase I

- Homologous chromosomes split and move to opposite sides of the cell

Stages of Meiosis

Meiosis I:

Metaphase I

- Tetrads (homologous chromosomes) line up along the equator of the cell

- Independent Assortment- The way in which the chromosomes line up is random,

thus creating 223 different possibilities.

- Nuclear membrane dissolves

- Spindle fibers form

- DNA winds up

- Synapsis occurs: Homologous chromosomes create pairs

- Synapsis allows crossing over to occur.

- Crossing over: The arms of the homologous chromosomes

overlap and break off, forming a new combination of genes.

- This creates genetic diversity.

Stages of Meiosis

Meiosis I:

Prophase I

- Copies of DNA

- Growth of cell

Stages of Meiosis

Meiosis I:

Interphase

Meiosis Diagram

- Meiosis II follows the same process as mitosis, but with half the number of

chromosomes. The 2 haploid cells produced from Meiosis I go under another cell

division identical to that of mitosis, thus producing 4 daughter cells with only half the

amount of chromosomes as the parent.

Stages of Meiosis

Meiosis II

- Cell pinches inward

- Nuclear membrane will reform

- DNA may unwind

Stages of Meiosis

Meiosis I:

Telophase I

II. Genetics

Gregor Mendel (the father of genetics) created 4 major ideas of genetics:

1. The Law of Dominance

- Some alleles are dominant while others are recessive. Dominant alleles mask the

recessive ones.

2. 2 genes for every trait (1 mom, 1 dad)

- Usually 2 alleles: one dominant, one recessive

3. The Law of Segregation

- For each trait the 2 genes are separated; only one gets passed on

4. The Law of Independent Assortment

- Different traits don't influence each other as they are passed on

Gregor Mendel

Oogensis is the creation of ovum (egg cells) in the ovaries. It begins with a diploid

oogonium and results in a haploid egg cell. Oogensis also creates 3 polar bodies, which

are much smaller than the ovum and eventually degenerate. The production of one egg

cell via oogenesis normally occurs only once a month, from puberty to menopause.

Oogenesis

Spermatogenesis is the creation of sperm in the testes. It begins with a diploid

spermatogenium and results in 4 haploid sperm cells.

Spermatogenesis

During meiosis, reduction division produces 4 haploid cells from 1 diploid cell. It is

essentially another name for meiosis.

Reduction

Division

Blood Types There are 4 different blood types with 3 different alleles:

A (IAIA or IAi),

B (IBIB or IBi),

AB (IAIB),

O (ii)

In epistasis, one gene controls the expression of another gene. One gene could hide the

expression of another gene.

Baldness is epistatic to widow's peak; if someone is bald, you wouldn't be able to see the

widow's peak anyway.

Epistasis

If two traits are codominant, neither of them are dominant over the other. If a gene is

heterozygous with 2 codominant traits, instead of showing one or the other, it will

instead show almost a combination of the two.

For example, red (RR) and white (R'R') may be codominant in plants.

RR= Red

R'R'= White

RR' or R'R= Pink

Codominance

A sex chromosome is a chromosome involved with determining the sex of an organism. Sex Chromosome

An autosome is any chromosome that is not a sex chromosome. Autosome

If a trait is homozygous, it has 2 identical alleles.

It can be homozygous dominant or homozygous recessive (BB or bb).

A heterozygous trait has 2 different alleles. It is sometimes referred to as a hybrid.

Bb

Homozygous vs.

Heterozygous

Traits can be inherited, acquired, sex-linked, or polygenic.

An inherited trait is a characteristic or gene genetically inherited/passed down from

generation to generation.

An acquired trait is a physical characteristic that is not inherited but may be an effect of

the environment or of a somatic mutation. Acquired traits are not passed down to

another generation.

A sex-linked trait is a trait associated with a gene that is carried only by the male or

female parent. For example, the colorblindness gene is only carried by the

X Chromosome.

A polygenic trait is a trait that is determined by more than one gene.

Traits

The phenotype refers to the set of observable characteristics of an individual.

Using the above FfDd x FfDd example, we find that the phenotypic ratio would be:

9 Freckled, Dimples: 3 Freckled, no Dimples: 3 not Freckled, Dimples: 1 not Freckled no

Dimples

Phenotype

The genotype refers to the different alleles an individual has.

For example, the genotypic ratio of a FfDd x FfDd cross would be:

1FFDD: 2FFDd: 2FfDD: 4FfDd: 1 FFdd: 2 Ffdd: 1 ffDD: 2ffDd: 1ffdd

Genotype

III. Evolution

Analagous structures have closely related functions but do not derive from the same

ancestral structure.

Analogous

Structures

Homologous structures are anatomical structures that occur in different species and that

originated by heredity from a structure in the most recent common ancestor of the

species.

Homologous

Structures

The Law of Superposition is a general law stating that in any sequence of sediments or

rocks that has not been overturned, the youngest sediments or rocks are at the top of the

sequence and the oldest are at the bottom.

Law of

Superposition

Fossils of species embedded in old rock are different than fossils in newer rocks.

Fossil Record

A new population in a new environment undergoes divergent evolution until it fills the

different niches of the environment.

Example: Darwin's finches

Adaptive

Radiation

An isotope of an element that emits energy in the form of streams of particles, owing to

the decaying of its unstable atoms.

Used in dating; C14will decay into C12.

C12’s half–life is 5730 years. This limits the dating

method to about 50000 years.

Potassium–Argon method – Used to date rocks. Half life is 1.2 billion years.

Rubidium–Strontium method – beta decay of Rubidium87 to Strontium87.

Used to check Potassium Argon method.

Radioactive

Isotopes + Dating

‘Survival of the fittest’ – Only the ones suited to the environment the best will survive.

Natural Selection

One might receive advantageous characteristics that enable it to survive better than

those who do not. They will survive to reproduce, which will eventually lead to a stronger

population.

Advantages of

Sexual

Reproduction

Darwin's Ideas Natural selection – survival of the fittest, inheritance of genes.

Three biological laws: environmental influence on organ development, change in body

structure based on use and disuse of parts, and the inheritance of acquired

characteristics.

Lamarck's Ideas

Evolution that begins with a common ancestor. Divergent

Evolution

Evolution of species that gradually resemble each other, even though there is no

common ancestor.

ancestor.

Convergent

Evolution

Deaths are concentrated in the middle of the range of phenotypes. The extreme forms of

the trait are favored.

Disruptive

Selection

Movement out of a population. Emigration

Movement into a population. Immigration

Allele frequencies change as a result of random events or chance. This can have a HUGE

impact on smaller populations.

Genetic Drift

A basic biological classification and containing individuals that resemble one another

and that may interbreed.

Species

Species can't mate because they are separated by natural barriers like mountains or

rivers.

Geographic

Isolation

Speciation happens in bursts – everything is in equilibrium for a while and then short

periods of time show rapid change.

Punctuated

Equilibrium

Factors to keep allele frequencies constant:

- Random Mating

- Large Populations

- No immigration/emigration

- Not mutations

- No natural selection

Genetic

Equilibrium

The gene pool consists of all genes including all of the alleles present in a population. Gene Pool

- Fossil Record

- Biochemical Evidence

- Structural Evidence

- Embryological Evidence

- Geographic Distribution

Evidence of

Evolution

In 1953, Stanley L. Miller and Harold C. Urey at the University of Chicago devised an

experiment to mimic the conditions then thought to have existed on Earth before living

organisms. They put methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O)

in a beaker and ran electric current through it (to simulate lighting).

After a week, they found that a significant part of the raw materials had formed organic

compounds, including some amino acids. The importance of the experiment was that

compounds important to life could form readily on a pre-biotic Earth.

Miller-Urey

Experiment

Mutations cause variety, and that variety is what helps the organism change over time.

The new genes introduced by mutations may produce better adaptation to the habitat.

Importance of

Mutations to

Evolution

Evolution is the change in species over time. It only happens in populations, NOT

individuals.

Definition of

Evolution

The struggle between organisms of the same or different species for limited resources

such as food or light.

Competition

A vestigial structure is a structure that once was useful in an animal’s evolutionary past,

but that now is useless or very close to useless.

Vestigial

Structures

Two organisms that have a close ecological relationship affect the evolution of each

other.

Example: Plants+Bees, Humans+Antibiotic resistant bacteria

Coevolution

IV. Classification

fication

Plants

- Eukaryotic

- Autotrophic

- Found in water and on land

- Cell walls made of cellulose and contain chloroplasts

- Multicellular

- Mosses, Ferns, Cones and Flowers

Animals

- Eukaryotic

- Heterotrophs

- Found all over

- No cell walls and no chloroplasts

- Most can move for at least a part of their life cycle

- Multicellular

- Vertebrates and invertebrates

- Sponges, worms, insects, fish, amphibians, reptiles, birds, mammals

Protists

- Eukaryotic

- Autotrophs or Heterotrophs

- Animal Like: Heterotrophs

- Fungi Like: Absorb nutrients outside of their bodies

- Plant Like: Photosynthesis

- Survive in moist environments

- Many have varied ways of locomotion

- Very Varied!

- Cell walls made of cellulose

- Most unicellular but some multicellular

- Amoebas, slime molds, paramecium, giant kelp, algae

The 6 Kingdoms:

Plants

Animals

Protists

Fungi

Archaebacteria

Eubacteria

Carolus Linnaeus was a Swedish botanist who laid the foundations for binomial

nomenclature. He is considered as the originator of modern scientific classification of

plants and animals.

Carolus (Carl)

Linnaeus

Kingdom, Phylum, Class, Order, Family, Genus, Species

Keep Pond Clean Or Froggy Gets Sick

Kids Playing Catch On Freeways Get Smashed

Hierarchical List

of Taxa

Binomial nomenclature is a system of naming organisms. It consists of 2 parts: the

genus and the species. It is usually underlined or italicized.

The genus is capitalized, and the species is not.

Genus species

Panthera tigris

Homo sapiens

Binomial

Nomenclature

A phylogenetic tree shows evolutionary relationship between groups of organisms

Characteristics Used

- Fossil Record

- Morphology (homologous structures)

- Embryological Development

- Chromosomes and Macromolecules

Phylogenetic Tree

Fungi

- Eukaryotic

- Heterotrophs- Absorb nutrients outside of body

- Cell Walls made of chitin

- Most mutlicellular but some unicellular

- Found on decaying material (decomposers) or on living material (parasitic)

- Common molds, Sac Fungi, Club Fungi, Imperfect Fungi

Archaebacteria

- Prokaryote

- Autotroph or heterotroph

- Lives in harsh environments

- Volcanic hot springs

- Some can only survive in environments without oxygen

- Cell walls have no peptidoglycan

- Cell membranes have unique lipids not found in any other organism

- Single cellular

- More similar to Eukaryotes

- Methanogens

Eubacteria

- Prokaryotic

- Heterotroph or Autotroph

- All over

- Some found in soil

- others deadly parasites

- Some need oxygen, others are poisoned by oxygen

- Cell walls contain peptidoglycan

- Single Cellular- Three shapes! Rods, spirals and spheres

- Strep throat and E Coli

The 6 Kingdoms:

Plants

Animals

Protists

Fungi

Archaebacteria

Eubacteria

V. Ecology

There are 2 types of growth: exponential and logistic.

Population Growth

The purpose of food chains and food webs is to show how animals interact as predators

and prey in an environment. They also show the flow of energy in a population.

Food Chain/Web

Human

Classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: Homo sapiens

Exponential Logistic In exponential growth, as the time increases, the population also increases. This continues

indefinitely. However, in logistic growth, the population will increase until it reaches its carrying capacity, K. When it reaches K, the growth

levels out and maintains consistent.

There are many factors that can limit the growth of a population. There are 2 main

types: density dependent and density independent.

Density dependent factors include: Competition, Predation, Disease, and Parasites

Density independent factors include: Weather, Natural Disasters, and Human

Factors (damming rivers, deforestation, controlled burns)

Unless there are no limiting factors, populations tend to follow logistic growth.

Remember what happened to the Kaibab deer? Their natural predators were taken

away, thus booming the growth of the deer. However, when they overshot the

carrying capacity, they soon ran out of resources and many died.

Consumers also go on different trophic levels. There are the primary consumers which

eat the producers, the secondary consumers which eat the primary consumers, and so

on.

Consumers

The producer is the first trophic level in a food chain in which it serves as a food source

for consumers or for higher trophic levels.

Producer

Abiotic factors are the nonliving components of the environment. These are the physical

and chemical characteristics of the environment.

Abiotic Factors

Biotic factors are the living components of the environment. They include all of the living

things that affect the organism.

Biotic Factors

A niche is the specific role, or way of life, of a species within its environment. It includes

the range of conditions that the species can tolerate, the resources it uses, the methods

by which it obtains resources, the number of offspring it has, its time of reproduction,

and all other interactions with its environment.

Niche

A habitat is the place where an organism lives. Habitat

Biosphere ---> Ecosystem ---> Community ---> Population ---> Organism Levels of

Organization

The carrying capacity is the number of people, other living organisms, or crops that a

region can support without environmental degradation.

Carrying Capacity

One organism hunts and feeds on another organism. This benefits the predator but hurts

the prey.

Example: Cheetahs hunt, kill, and eat gazelles.

Symbiotic

Relationships:

Predation :D :(

Two organisms compete over food, land, etc. This benefits neither organism.

Example: Two elephant seals will fight, often violently, in order to gain the attention of a

female.

Symbiotic

Relationships:

Competition :( :(

A parasitic relationship is one in which one organism is benefited while the other is

harmed.

Example: Ticks feed on deer blood.

Symbiotic

Relationships:

Parasitism :D :(

Commensalism is a relationship between two organisms where one benefits and the

other is not significantly harmed or helped.

Example: Hermit crabs live in shells made and then abandoned by snails. This neither

harms not benefits the snails.

Symbiotic

Relationships:

Commensalism

:D :|

Symbiotic

Relationships:

Mutualism :D :D

Mutualism is a relationship between individuals of different species where both

individuals benefit.

Example: oxpeckers feed on the ticks found on a rhinoceros.

Symbiosis Symbiosis is the interaction between two different organisms living in close physical

association. There are 5 main kinds of symbiotic relationships.

Population density is the measure of the amount of organisms in a given area. Population

Density

Water will

evaporate from

the lakes and

oceans into the

air, then

condense and fall

back to earth,

where it runs off

into another body

of water to be

taken in by

plants. The

plants will give

off a little water,

evaporation

occurs, and the

cycle starts again.

The Water Cycle

Ecology is the study of the interactions between organisms and the living and nonliving

components of their environment. It is a broad science that involves collecting

information about organisms and their environments, observing and measure

interactions, looking for patterns, and seeking to explain these patterns.

What is Ecology?

Of course, there's energy in an environment. But how does it cycle through?

Energy starts at the sun, then moves to a producer/autotroph. It then moves to a

heterotroph, which could be anything from an herbivore to an omnivore to a

decomposer. As energy moves up trophic levels, 90% of it is used. Only 10% of the

energy goes up each step. This is why an owl on the top of a food chain needs a LOT of

grass on the bottom to feed it.

Energy Flow

Trophic levels are the feeding positions on a food chain. These include producers (1st),

primary consumers (2nd), secondary consumers (3rd), and so on.

Trophic Levels

Decomposer A decomposer is an organism that decomposes organic material by feeding on dead or

decaying organisms, thus recycling the nutrients.

Omnivore An omnivore is an organism that feeds on both plants and animals.

A carnivore is an organism that feeds on animals. Carnivore

An herbivore is an organism that feeds on plants. Herbivore

Nitrogen is crucial

for living

organisms so that

they will be able to

make amino acids

necessary for

proteins. Nitrogen

must be converted

into ammonia

NH3 or nitrite and

nitrate ions, NO2-

and NO3-. Some

bacteria convert N2

(nitrogen) into

ammonia through

nitrogen fixation.

Nitrogen can

return to the

atmosphere when

bacteria convert

the nitrites and

nitrates back into

N2 by

denitrification.

The Nitrogen

Cycle

There are 4 major

ways in which

carbon can cycle

through the

environment:

biological

processes from

living organisms,

geochemical

processes from the

earth,

biogeochemical

processes from the

combination of the

two, and human

activity. Carbon

enters the

atmosphere via

respiration,

volcanic eruptions,

burning fossil

fuels/forests, and

CO2 dissolved in

oceans is released.

The Carbon Cycle

VI. The Systems

The Mouth

- Mechanical Digestion: Teeth break up food

- Chemical Digestion: Saliva (a mixture of water, mucus, and salivary amylase)

- Salivary amylase breaks down starch into disaccharide maltose

- Chews food into bolus

The Salivary Glands

- Parotid, Submandibular, Sublingual

- Create saliva for chemical digestion

The digestive system is responsible for the breaking down of food into molecules that the

body can absorb and use.

Purpose

- Ingest, Digest, Absorb, Eliminate

2 Parts

- Gastrointestinal tract (Alimentary canal)

- Starts at mouth and ends at anus

- Accessory Organs

- Food doesn't pass through but they aide in the digestive process

- Salivary glands, pancreas, liver, gallbladder

The Digestive

System

The Epiglottis

- Responsible for covering up your windpipe when you swallow so you don't choke

The Esophagus

- Transports food to the stomach

- Peristalsis is here

The Stomach

- Food passes through the cardiac sphincter to enter the stomach

- Can stretch and hold up to 2L

- Mechanical digestion: Contents are churned

- Chemical digestion: Pepsin (Pepsinogen turned into this in the presence of HCl)

- Protected by mucus

- Pyloric sphincter leads to small intestine

- Chyme is produced when food particles are broken up and mixed with gastric fluids

The Small Intestine

- Chemical digestion: Enzymes break down peptides into amino acids, disaccharides into

monosaccharides, and fats into glycerol and fatty acids

- Maltase produced in small intestine, although amylase, trypsin, and lipase come

from the pancreas to help

- During absorption, the end products of digestion - amino acids, monosaccharides,

glycerol, and fatty acids - are transferred into the circulatory system through blood and

lymph vessels in the lining of the small intestine

- Millions of villi greatly expand the surface area (size of a tennis court!)

- Nutrients absorbed by diffusion and active transport

- Lacteals are capillaries and tiny lymph vessels inside

each of the villi

- Fatty acids enter lacteals and are carried to the

bloodstream

The Large Intestine AKA Colon

- Reabsorbs water

- Too much? Diarrhea

- Too little? Constipation

- Bacteria! - E. coli

- Helps break up cellulose in fruits and veggies

- Produces Vitamins K and B

- Creates gases

The Rectum

- Holds waste ready for disposal

The Anus

- Helps move bowel waste out of the body

The Digestive

System

The circulatory system is used to deliver oxygen and nutrients to the cells and remove

waste.

Parts

- Cardiovascular system

- Heart

- Blood Vessels

- Arteries

- Veins

- Blood

- Lymphatic system

The Circulatory

System

The Liver

- Produces bile

- Breaks down fats

- Detoxifies

- Stores extra glucose as glycogen

- Makes proteins

Gallbladder

- Stores bile until needed

Pancreas

- Produces important digestive juices

for the small intestine

- Amylase: carbs

- Chemotrypsin: proteins

- Trypsin: proteins

- Lipase: lipids

- Produces hormones to help the body

- Glucagon: Stimulates the liver to break down glycogen to raise blood sugar

- Insulin: Stimulates the liver to store more glucose as glycogen to lower blood

sugar

- Produces sodium bicarbonate

- Neutralizes stomach acid in the small intestine

Appendix

- A vestigial organ

- May be involved in storing good bacteria

The Digestive

System

The Circulatory

System

Erythrocytes (Red Blood Cells)

- Transports oxygen

- Made in marrow

- Live 120 days

- Hemoglobin attaches to the oxygen

- No nucleus

- 30 trillion in body, 2 million die every second

Leukocytes (White Blood Cells)

- Large

- Less numerous than erythrocytes

- Has nucleus

- Made in marrow

- 5 types: Basophil, Neutrophil, Eosinphil, Monocytes, Lymphocytes

Platelets

- Cell fragments

- From bone marrow

- Help with blood clotting

- Short life span

Plasma

- The fluid around the blood

- 55% of blood

Arteries vs. Veins

ARTERIES

VEINS

Carry blood away from the heart Carry blood towards the heart

Carry oxygenated blood Carry deoxygenated blood

Hold bright red blood Hold dark red blood

Blood at high pressure Blood at low pressure

Blood is frothy or spurts Blood oozes

Thick walls Thin walls

Usually deep Usually close the surface but can be deep

No valves Valves (to assist flow to the heart)

Pulse No pulse

Elastic/muscular Not elastic/muscular

Served by many nerves Served by few nerves

Fewer in number Greater in number

Path of Blood Flow

1. Blood enters the heart from the body through the superior and inferior vena cavas.

2. Blood is deposited into the right atrium and is squeezed into the right ventricle.

3. Blood leaves the right ventricle through the pulmonary artery and is sent to the lungs

to pick up oxygen.

4. Blood leaves the lungs and comes back to the heart via the pulmonary vein.

5. Blood is deposited into the left atrium and is squeezed into the left ventricle.

6. Blood is pumped out of the left ventricle through the aorta and is sent to the rest of the

body.

SA Node, AV Node, Heartbeat

- SA Node= pacemaker

- Electrical impulse causes atria to contract

- Sends impulse to AV node which causes ventricles to contract

- Heartbeat has 2 phases:

- Systole: Ventricles contract, AV valves close, SL valves open, blood leaves

- Diastole: Ventricles relax, AV valves open, SL valves close

- Makes "Lub Dub" sound

The Circulatory

System

Atria

- The main function of the atria is to receive blood and squeeze blood into the ventricles.

- Right: Deoxygenated blood from the vena cavas.

- Left: Oxygenated blood from the pulmonary veins.

Ventricles

- The main function of the ventricles is to send out blood.

Septum

- The septum separates the two sides of the heart. It prevents blood crossing from one

side of the heart to the other.

Spleen

- Removes old red blood cells and stores extra red blood cells.

Liver

- The liver removes old red blood cells and detoxifies substances.

Types of Blood Vessels

- Arteries

- Arterioles

- Capillaries

- Smallest vessels that allow for gas exchange with the cells around them

- Point where the arteries become veins

- Venules

- Veins

The Circulatory

System

Nostrils

Air enters and is warmed Common passage for air and food

Protects trachea from food while swallowing

Voice box- holds the vocal chords

Wind pipe- protected by rings of cartilage

Right+left bronchus take oxygen to lungs

Smaller passageways that branch of bronchi

Thin-walled air sacs where the gas exchange occurs

Structure of muscle that holds all of the tubes together and opens

and constricts the air passages when necessary

Muscle that causes breathing

Controls rate of breathing

Sweeps mucus out of lungs

Moistens the air and traps dust particles

Protects lungs

Nares

Nasal Cavity

Pharynx Epiglottis

Larynx

Trachea

Bronchi

Bronchioles

Alveoli

Lung

Diaphragm

Medulla

Oblongata

Cilia

Mucus

Rib Cage

The purpose of the respiratory system is to exchange oxygen and carbon dioxide with the

body and environment.

The Respiratory

System

Tip:

The adjective renal

is from the Latin

term renalis,

meaning of or near

the kidneys.

Flow of Waste

1. Kidney: filters water, urea (converted from ammonia by the liver), salts, glucose,

amino acids, yellow bile compounds, and other trace substances from the blood

- Less than 1% of the water and other materials remain behind to be excreted as

waste products

2. The above materials pass from the nephrons (in the kidneys) to the renal pelvis.

3. From the renal pelvis, waste trickles out of the kidney into the ureter.

4. The ureter empties into the urinary bladder, where a ringlike sphincter prevents

spontaneous emptying.

5. When ready to expel urine, the sphincter relaxes and the urine flows from the bladder

to the urethra to the (hopefully) toilet bowl.

The Excretory

System

Inspiration

- Breathing in (inhalation)

- Active process

- Caused by muscular contraction of the diaphragm and intercostal muscles

Expiration

- Breathing out (exhalation)

- Typically passive process

- Caused by recoil of diaphragm

Exchange of Oxygen and Carbon Dioxide

- Takes place in the millions of alveoli in our lungs

- Oxygen in the alveoli is diffused into the blood in the capillaries, and CO2 from the

blood in the capillaries moves to the alveoli. From there, the oxygen is taken back to the

heart where it is pumped to the rest of the body and the carbon dioxide is exhaled from

the lungs.

The Respiratory

System