Bio Final Review

Front 1

Three modes of selection:

Back 1

-Directional selection favors individuals at one end of the phenotypic range
-Disruptive selection favors individuals at both extremes of the phenotypic range
-Stabilizing selection favors intermediate variants and acts against extreme phenotypes

Front 2

Hardy-Weinberg

Back 2

equation can be used to test whether a population is evolving
p+q=1

○ 320 red flowers (CRCR)
○ _160 pink flowers (C^RC^W)______________
○ 200 white flowers (CWCW)
– Calculate the number of copies of each allele:
○ CR = (320 ´ 2) + 160 = 800
○ CW = (20 ´ 2) + 160 = 200
– To calculate the frequency of each allele:
○ _p=freq C^R=800/(800+200)______________
○ q = freq CW = 200 / (800 + 200) = 0.2
– The sum of alleles is always 1

0.8 + 0.2 = 1

• The Hardy-Weinberg principle describes a population that is not evolving

○ p2 + 2pq + q2 = 1

where p2 and q2 represent the frequencies of the homozygous genotypes and 2pq represents the frequency of the heterozygous genotype

Front 3

The five conditions for nonevolving populations are rarely met in nature:

Back 3

◊ No mutations
◊ Random mating
◊ No natural selection
◊ Extremely large population size
◊ No gene flow

Front 4

Natural selection

Back 4

-Natural selection is the only mechanism that consistently causes adaptive evolution
– Gene flow tends to reduce variation among populations over time

Front 5

Biological Species Concept

Back 5

(one way to divide species):

-A species is a group of populations whose members can breed and produce viable, fertile offspring

-Ability to mate = formation of a species

-Gene flow between populations holds together the phenotype of a population (ongoing exchange of alleles)

-The biological species concept emphasizes absence of gene flow

Front 6

Other Definitions of Species

Back 6

1. morphological species concept:
-A species is characterized by its body shape
-It applies to sexual and asexual species but relies on subjective criteria
2. ecological species concept:
-A species is characterized by its ecological niche
-It applies to sexual and asexual species and emphasizes the role of disruptive selection
3. phylogenetic species concept:
-A species is the smallest group of individuals that share a common ancestor
-It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species

Front 7

Speciation can occur in two ways:

Back 7

Allopatric speciation
Sympatric speciation

-In a sympatric speciation, various factors can limit gene flow:
-Polyploidy
-Habitat differentiation
-Sexual selection

Front 8

radiometric dating

Back 8

-The absolute ages of fossils can be determined by radiometric dating
-A “parent” isotope decays to a “daughter” isotope at a constant rate
-Each isotope has a known half-life, the time required for half the parent isotope to decay
-Radiocarbon dating can be used to date fossils up to 75,000 years old
-For older fossils, some isotopes can be used to date sedimentary rock layers above and below the fossil

Front 9

Geological record

Back 9

Front 10

endosymbiont theory

Back 10

-The endosymbiont theory proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells
-An endosymbiont is a cell that lives within a host cell

Front 11

Key evidence supporting an endosymbiotic origin of mitochondria and plastids:

Back 11

-Inner membranes are similar to plasma membranes of prokaryotes
-Division is similar in these organelles and some prokaryotes
-These organelles transcribe and translate their own DNA
-Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes

Front 12

Plate Tectonics

Back 12

-At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago
-According to the theory of plate tectonics, Earth’s crust is composed of plates floating on Earth’s mantle
-Tectonic plates move slowly through the process of continental drift
-Oceanic and continental plates can collide, separate, or slide past each other
-Interactions between plates cause the formation of mountains and islands, and earthquakes

Front 13

Consequences of Continental Drift

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-Formation of the supercontinent Pangaea about 250 million years ago had many effects
--A deepening of ocean basins
--A reduction in shallow water habitat
--A colder and drier climate inland

Front 14

Hierarchial Classification

Back 14

Domain, Kingdom, Phylum, Class, Order, family, genus, species

Front 15

Alternation of Generations and Multicellular, Dependent Embryos

Back 15

-Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations
-The gametophyte is haploid and produces haploid gametes by mitosis
-Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis
-The diploid embryo is retained within the tissue of the female gametophyte
-Nutrients are transferred from parent to embryo through placental transfer cells
-Land plants are called embryophytes because of the dependency of the embryo on the parent

Front 16

Walled Spores Produced in Sporangia

Back 16

-The sporophyte produces spores in organs called sporangia
-Diploid cells called sporocytes undergo meiosis to generate haploid spores
-Spore walls contain sporopollenin, which makes them resistant to harsh environments

Front 17

Multicellular Gametangia

Back 17

-Gametes are produced within organs called gametangia
-Female gametangia, called archegonia, produce eggs and are the site of fertilization
-Male gametangia, called antheridia, produce and release sperm

Front 18

Apical Meristems

Back 18

-Plants sustain continual growth in their apical meristems
-Cells from the apical meristems differentiate into various tissues

Front 19

Additional derived traits include

Back 19

-Cuticle, a waxy covering of the epidermis
-Mycorrhizae, symbiotic associations between fungi and land plants that may have helped plants without true roots to obtain nutrients
-Secondary compounds that deter herbivores and parasites

Front 20

vascular tissue

Back 20

-Land plants can be informally grouped based on the presence or absence of vascular tissue
-Most plants have vascular tissue; these constitute the vascular plants
-Nonvascular plants are commonly called bryophytes
-Bryophytes are not a monophyletic group; their relationships to each other and to vascular plants is unresolved
-Seedless vascular plants can be divided into clades
-Lycophytes (club mosses and their relatives)
-Pterophytes (ferns and their relatives)
-Seedless vascular plants are paraphyletic, and are of the same level of biological organization, or grade

Front 21

Mosses and other nonvascular plants have life cycles dominated by gametophytes

Back 21

-Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants
+Liverworts, phylum Hepatophyta
+Hornworts, phylum Anthocerophyta
+Mosses, phylum Bryophyta

Front 22

Moss Life Cycle(Gametophyte)

Back 22

-A spore germinates into a gametophyte composed of a protonema and gamete-producing gametophore
The height of gametophytes is constrained by lack of vascular tissues
-Rhizoids anchor gametophytes to substrate
-Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium
-Sperm swim through a film of water to reach and fertilize the egg

Front 23

Fern Life Cycle (sporophyte)

Back 23

- Sporangia Release spores that develop into gametophytes
- Each gametophyte develops sperm-producing organs called antheridia and egg producing archegonia
- Sperm use flagella to swim to the eggs in the archegonia
- A zygote develops into a new sporophyte and grows out of the gametophyte

-On the underside of the sporophyte's reproductive leaves are spots called sori.

Front 24

Five Derived Traits of Seed Plants

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Front 25

Plant Groups

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Front 26

Flower structure

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Front 27

monocots and dicots

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Front 28

Embryonic development

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Front 29

Symmetry

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Front 30

Diploblastic

Back 30

animals have ectoderm and endoderm
-These include cnidarians and comb jellies

Front 31

Triploblastic

Back 31

animals also have an intervening mesoderm layer; these include all bilaterians
-These include flatworms, arthropods, vertebrates, and others

Front 32

Body Cavities

Back 32

-Most triploblastic animals possess a body cavity
-A true body cavity is called a coelom and is derived from mesoderm
-Coelomates are animals that possess a true coelom
-A pseudocoelom is a body cavity derived from the mesoderm and endoderm
-Triploblastic animals that possess a pseudocoelom are called pseudocoelomates
-Triploblastic animals that lack a body cavity are called acoelomates

Front 33

Proto vs Deuter

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Front 34

Most eudicots and gymnosperms have a taproot system, which consists of:

Back 34

-A taproot, the main vertical root
-Lateral roots, or branch roots, that arise from the taproot

Front 35

Most monocots have a fibrous root system, which consists of:

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Adventitious roots that arise from stems or leaves
Lateral roots that arise from the adventitious roots

Front 36

Root structure

Back 36

Front 37

Stem Structure

Back 37

Front 38

Pollination

Back 38

-In angiosperms, pollination is the transfer of pollen from an anther to a stigma
-Pollination can be by wind, water, or animals
-Wind-pollinated species (e.g., grasses and many trees) release large amounts of pollen

Front 39

Fruits

Back 39

Front 40

Exchange with the Enviornment

Back 40

Front 41

Feedback control maintains the internal environment in many animals

Back 41

-A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
-A conformer allows its internal condition to vary with certain external changes
-For a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response
-The response returns the variable to the set point
-The dynamic equilibrium of homeostasis is maintained by negative feedback, which helps to return a variable to a normal range
-Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off
-Positive feedback amplifies a stimulus and does not usually contribute to homeostasis in animals
-Homeostasis can adjust to changes in external environment, a process called acclimatization

Front 42

Homeostatic processes for thermoregulation involve form, function, and behavior

Back 42

-Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range
The body temperature of a poikilotherm varies with its environment
-The body temperature of a homeotherm is relatively constant
-The relationship between heat source and body temperature is not fixed (that is, not all poikilotherms are ectotherms)
-Five adaptations help animals thermoregulate:
=Insulation
=Circulatory adaptations
=Cooling by evaporative heat loss
=Behavioral responses
=Adjusting metabolic heat production

Front 43

countercurrent exchange

Back 43

-Countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and reduce heat loss

Front 44

Thermogenesis

Back 44

--the adjustment of metabolic heat production to maintain body temperature
-Thermogenesis is increased by muscle activity such as moving or shivering
-Nonshivering thermogenesis takes place when hormones cause mitochondria to increase their metabolic activity
-Some ectotherms can also shiver to increase body temperature
-Thermoregulation is controlled by a region of the brain called the hypothalamus
-The hypothalamus triggers heat loss or heat generating mechanisms
-Fever is the result of a change to the set point for a biological thermostat

Front 45

Single and Double Circulation

Back 45

-Bony fishes, rays, and sharks have single circulation with a two-chambered heart
-In single circulation, blood leaving the heart passes through two capillary beds before returning
-Amphibian, reptiles, and mammals have double circulation
-Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart
-In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs
-In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin
-Oxygen-rich blood delivers oxygen through the systemic circuit
-Double circulation maintains higher blood pressure in the organs than does single circulation

Front 46

Amphibians

Back 46

-Frogs and other amphibians have a three-chambered heart: two atria and one ventricle
-The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit
-When underwater, blood flow to the lungs is nearly shut off

Front 47

Reptiles (Except Birds)

Back 47

-Turtles, snakes, and lizards have a three-chambered heart: two atria and one ventricle
-In alligators, caimans, and other crocodilians a septum divides the ventricle
-Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit

Front 48

Mammals and Birds

Back 48

-Mammals and birds have a four-chambered heart with two atria and two ventricles
-The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood
-Mammals and birds are endotherms and require more O2 than ectotherms

Front 49

Mammalian Circulation

Back 49

§ Right ventrical
§ Simelunar valve
§ Pulmonary arteries
§ Lungs-capillary beds-loads O2 and unloads CO2
§ Pulmonary veins
§ Left atrium
§ Atrioventricular valve
§ Left ventrical
§ Semilunar valve
§ Aorta
§ Coronary arteries (to heart)
§ Capillary beds in head and arms
§ Capillary beds in the abdominal organs and legs
§ Capillaries rejoin, form venules, then veins
§ Superior vena cava
§ Inferior vena cava
§ Right atrium
§ Atrioventricular valve

Front 50

Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets

Back 50

Front 51

Respiratory system

Back 51

-Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs
-Exhaled air passes over the vocal cords in the larynx to create sounds
-Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx
Gas exchange takes place in alveoli, air sacs at the tips of bronchioles
-Oxygen diffuses through the moist film of the epithelium and into capillaries
-Carbon dioxide diffuses from the capillaries across the epithelium and into the air space

Front 52

Osmoregulation balances the uptake and loss of water and solutes

Back 52

-Cells require a balance between uptake and loss of water
-Osmolarity, the solute concentration of a solution, determines the movement of water across a selectively permeable membrane
-If two solutions are isoosmotic, the movement of water is equal in both directions
-If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution
-Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity
-Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
-Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity
-Euryhaline animals can survive large fluctuations in external osmolarity

Front 53

Marine Animals

Back 53

-Most marine invertebrates are osmoconformers
-Most marine vertebrates and some invertebrates are osmoregulators
-Marine bony fishes are hypoosmotic to sea water
-They lose water by osmosis and gain salt by diffusion and from food
-They balance water loss by drinking seawater and excreting salts

Front 54

Transport Epithelia in Osmoregulation

Back 54

-Animals regulate the solute content of body fluid that bathes their cells
-Transport epithelia are epithelial cells that are specialized for moving solutes in specific directions
-They are typically arranged in complex tubular networks
-An example is in nasal glands of marine birds, which remove excess sodium chloride from the blood

Front 55

The nephron is organized for stepwise processing of blood filtrate

Back 55

-Proximal Tubule
=Reabsorption of ions, water, and nutrients takes place in the proximal tubule
=Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries
=Some toxic materials are actively secreted into the filtrate
=As the filtrate passes through the proximal tubule, materials to be excreted become concentrated
-Descending Limb of the Loop of Henle
=Reabsorption of water continues through channels formed by aquaporin proteins
=Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate
=The filtrate becomes increasingly concentrated
-Ascending Limb of the Loop of Henle
=In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid
=The filtrate becomes increasingly dilute

Front 56

Continued

Back 56

-Distal Tubule
=The distal tubule regulates the K+ and NaCl concentrations of body fluids
=The controlled movement of ions contributes to pH regulation
-Collecting Duct
=The collecting duct carries filtrate through the medulla to the renal pelvis
=One of the most important tasks is reabsorption of solutes and water
=Urine is hyperosmotic to body fluids

Front 57

The Two-Solute Model

Back 57

-In the proximal tubule, filtrate volume decreases, but its osmolarity remains the same
-The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney
-This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient
-Considerable energy is expended to maintain the osmotic gradient between the medulla and cortex
-The collecting duct conducts filtrate through the osmolarity gradient, and more water exits the filtrate by osmosis
-Urea diffuses out of the collecting duct as it traverses the inner medulla
-Urea and NaCl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood

Front 58

Nerves

Back 58

Front 59

Action potentials are the signals conducted by axons

Back 59

-Changes in membrane potential occur because neurons contain gated ion channels that open or close in response to stimuli
-When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative
-This is hyperpolarization, an increase in magnitude of the membrane potential
-Opening other types of ion channels triggers a depolarization, a reduction in the magnitude of the membrane potential
-For example, depolarization occurs if gated Na+ channels open and Na+ diffuses into the cell

Front 60

Graded Potentials and Action Potentials

Back 60

-Graded potentials are changes in polarization where the magnitude of the change varies with the strength of the stimulus
-These are not the nerve signals that travel along axons, but they do have an effect on the generation of nerve signals
-If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an action potential
-Action potentials have a constant magnitude, are all-or-none, and transmit signals over long distances
They arise because some ion channels are voltage-gated, opening or closing when the membrane potential passes a certain level

Front 61

Generation of Action Potentials: A Closer Look

Back 61

-An action potential can be considered as a series of stages
-At resting potential
=1.Most voltage-gated sodium (Na+) channels are closed; most of the voltage-gated potassium (K+) channels are also closed
-When an action potential is generated
2.Voltage-gated Na+ channels open first and Na+ flows into the cell
3.During the rising phase, the threshold is crossed, and the membrane potential increases
4.During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell
5.During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close and resting potential is restored

Front 62

Hearing

Back 62

-Vibrating objects create percussion waves in the air that cause the tympanic membrane to vibrate
-The three bones of the middle ear transmit the vibrations of moving air to the oval window on the cochlea
-These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal
-Pressure waves in the canal cause the basilar membrane to vibrate, bending its hair cells
-This bending of hair cells depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve
-The fluid waves dissipate when they strike the round window at the end of the tympanic canal

Front 63

The ear conveys information about

Back 63

-Volume, the amplitude of the sound wave
-Pitch, the frequency of the sound wave
-The cochlea can distinguish pitch because the basilar membrane is not uniform along its length
-Each region of the basilar membrane is tuned to a particular vibration frequency

Front 64

Several organs of the inner ear detect body movement, position, and balance

Back 64

-The utricle and saccule contain granules called otoliths that allow us to perceive position relative to gravity or linear movement
-Three semicircular canals contain fluid and can detect angular movement in any direction