Honors Biology Final Study Guide

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Griffith's experiment

-Griffith studied a bacterium called Streptococcus pneumoniae and was trying to develop a vaccine against a disease-causing strain of the bacterium
-each virulent bacterium is surrounded by a capsule
-the strain that is virulent (disease causing) grows as smooth-edged colonies and called the S strain
-the non-virulent strain lacks a capsule, and grows into rough colonies, so it is called the R strain
-Griffith used the two strains of S. pneumonaie on mice in his experiments:
-1. he injected R cells into a mouse, and the mouse lived
-2. he injected S cells into a mouse, and the mouse died
-3. he injected heat-killed S bacteria into the mouse, and the mouse survived
-4. mixed heat-killed S and R cells and injected it, and the mouse died, because the heat-killed S transforms the R cells

transformation

-Griffith concluded that heat-killed virulent bacterial cells release a hereditary factor that transfers the disease-causing ability to the live harmless cells
-this type of transfer of genetic material from one cell to another cell or from one organism to another organism is called transformation

Hershey-Chase experiment

-Hershey and Chase set out to test whether DNA or protein was the hereditary material viruses transfer when viruses enter a bacterium:
1. they used radioactive isotopes to label the protein and DNA in the phage
-they used radioactive sulfur (35S) to label protein and radioactive phosphorus (32P) to label DNA
-they allowed protein-labeled and DNA-labeled bacteria to separately infect E. coli
-2. they removed the phage coats from the cells in a blender
-3. used a centrifuge to separate the phage from the E. coli
-they found that all of the viral DNA and little of the protein had entered E. coli cells
-concluded that DNA is the hereditary molecule

DNA structure

-a nucleic acid made of two long chains (called strands) of repeating subunits called nucleotides
-each nucleotide consists of three parts:
-a five-carbon sugar
-called deoxyribose
-a phosphate group
-consists of a phosphorus (P) atom bonded to four oxygen (O) atoms
-a nitrogenous base
-contains nitrogen (N) atoms and carbon (C) atoms
-is a base (accepts hydrogen ions)

base pairing

-in DNA, cytosine on one strand pairs with guanine on the opposite strand
-and adenine pairs with thymine
-these pairs are called complementary bases
-A goes with T, G goes with C

DNA replication

-1. helicases separate the DNA strands
-2. DNA polymerases add complementary nucleotides, forming covalent bonds between the adjacent nucleotides
-3. DNA polymerases finish replicating the DNA and fall off

helicase

-an enzyme that separates the DNA strands in DNA replication
-it moves along the DNA molecule, breaking hydrogen bonds between the complementary nitrogenous bases
-this allows the 2 DNA strands of the double helix to separate from each other (the replication fork)

primase

enzyme that makes primer, and primer starts the DNA synthesis

DNA polymerase

-an enzyme that adds complementary nucleotides (found floating freely inside the nucleus) to each of the original strands in replication
-covalent bonds form between the deoxyribose sugar of one nucleotide and phosphate group of the next nucleotide on the growing strand
-hydrogen bonds form between the complementary nitrogenous bases on the original and new strands

ligase

-DNA replication leaves gaps in the newly synthesized strand
-ligase is an enzyme that joins the gaps together

semi-conservative replication

-a type of replication that describes DNA
-called this because each of the new DNA molecules has kept (or conserved) one of the two (or semi) original DNA strands

mutation

-a change in the nucleotide sequence of a DNA molecule
-when mistakes in DNA replication occur, the base sequence of the newly formed DNA differs from the base sequence of the original DNA
-can have serious effects on the function of an important gene and disrupt important cell functions

cancer

-sometimes, mutations that are not repaired can cause diseases such as cancer
-for example, mutations that affect genes that control how a cell divides can lead to an abnormal mass of cells called a tumor

central dogma

-the process of producing proteins is irreversible: a protein cannot be used to create DNA
-it goes DNA→RNA→protein

RNA

-ribonucleic acid
-the gene directs that making of the protein called melanin (a pigment) in hair follicle cells through an intermediate, which is RNA

differences between DNA and RNA

-RNA contains the sugar ribose, NOT the sugar deoxyribose found in DNA
-RNA contains the nitrogenous base uracil instead of the nitrogenous base thymine found in DNA
-RNA is usually single stranded rather than double stranded like DNA
-RNA is usually much shorter in length than DNA

three types of RNA-functions

-messenger RNA (mRNA):
-carries the genetic "message" from DNA in the nucleus to the ribosomesin the cytosol
-ribosomal RNA (rRNA):
-part of the structure of ribosomes (organelles in the cell where protein synthesis occurs)
-transfer RNA (tRNA):
-transfers amino acids to the ribosome to make a protein

transcription

-where DNA acts as a template for the synthesis of RNA
-occurs in three steps:
1. RNA polymerase (catalyzes the formation of RNA on a DNA template) binds to the promoter (initiates transcription)
-the DNA strands unwind and separate
2. RNA polymerase adds complementary nucleotides, resulting in an RNA molecule
-as RNA polymerase moves past, the separated DNA strands rewind
3. RNA polymerase reaches a termination signal (marks the end of a gene)
-RNA polymerase releases both the DNA and the newly formed RNA

how to use the genetic code

-three adjacent nucleotides ("letters") in mRNA specify an amino acid ("word") in a polypeptide
-first, you must translate the DNA into RNA
-the codon AUG acts as a start codon
-cetain sequences in mRNA (UAA, UAG, or UGA) called stop codons, signal for translation to end

translation

-where RNA directs the assembly of proteins
-each protein strand is made of polypeptides (chains of amino acids)
-occurs in five steps:
1. two ribosomal subunits, tRNA and mRNA join together
-enzymes attach a specific amino acid to one end of each tRNA according to the genetic code
-the other end of each tRNA contains three nucleotides on the RNA complementary to the sequence of codon in mRNA (anticodon)
2. a polypeptide chain is put together
-a tRNA with the appropriate amino acid pairs its anticodon with the second codon in mRNA
-ribosome detaches methionine from the 1st tRNA and a peptide bond forms between methionine and the second amino acid
-the first tRNA then exits the ribosome
3. the polypeptide chain continues to grow
4. the ribosome reaches the stop codon and the newly made polypeptide falls off
5. the ribosome complex falls apart, and the newly made polypeptide is released

spontaneous generation

-a process where living things could arise from nonliving things
-believed to be true before the 17th century
-it seemed to explain why maggots appeared on rotting meat and why fish appeared in ponds that were dry in the previous season

Redi's experiment

-Redi observed that tiny wormlike maggots turned into sturdy oval cases from which flies emerge
-he also observed that maggots seemed to appear where adult flies had previously landed
-his experimental group consisted of netting-covered jars that contained meat, to allow air to enter and prevent flies from landing on the meat
-the control group consisted of uncovered jars that also contained meat
-after a few days, maggots were living in the meat in the open jars, but the net-covered jars were maggot-free
-his experiment showed that flies come only from eggs laid by other flies

Pasteur's experiment

-Pasteur set out to clear up the issue of spontaneous generation
-he made a curve-necked flask that allowed the air inside the flask to mix with air outside, but it prevented solid parlicles (like microorganisms) from entering the flask
-he boiled broth in the flask, and the flasks remained clear for a year
-but when he broke the curved neck off, the flask became cloudy within a day

age of the earth

-the estimated age is more than 4 billion years
-to find it, scientists have explored Earth's surface and examined its many layers to establish a fairly complete picture of its geologic history
-early estimate's of Earth's age were made from studying layers of sedimentary rock in Earth's crust
-the age, however, couldn't be accurately estimated until the middle of the 20th century

isotope

atoms of the same element that differ in the number of neutrons they contain

half-life

-the length of time it takes for one-half of any size sample of an isotope to decay to a stable form
-how to find half-life:
-when an organism dies, decay of the existing carbon-14 continues
-after 5,730 years, half of the carbon-14 in a sample will have decayed
-after another 5,730 years, half of the remaining carbon-14 in the sample will have decayed
-but carbon-14 dating is limited to remains less than 60,000 years old

Miller-Urey experiment

-Miller and Urey used Oparin's hypothesis of how the Earth formed to set up their experiment
-their equipment had a chamber of gases (ammonia, hydrogen gas, water vapor, and compounds made of hydrogen and carbon, like methane)
-as the gases circulated in the chamber, electric sparks, substituting for lightning, supplied energy to drive chemical reactions
-the experiment produced a variety of organic compounds, including amino acids

chemosynthesis

-in this process, CO2 serves as a carbon source for the assembly of organic molecules
-energy is obtained from the oxidation of various inorganic substances, such as sulfur
-many species of archaea are autotrophs (or producers) that obtain energy this way, instead of photosynthesis

endosymbiotic theory

-the theory that between about 2.0 and 1.5 billion years ago, a type of small aerobic prokaryote was engulfed by and began to live and reproduce inside of a larger, anaerobic prokaryote
-the eukaryotes provided a beneficial environment and the prokaryotes provided a method of energy synthesis
-in a later case, photosynthetic cyanobacteria may have evolved into chloroplasts, which perform photosynthesis in modern eukaryotic plant and algae cells

catastrophism vs. uniforitarianism

-catastrophism:
-developed by Cuvier
-the idea that sudden geologic catastrophes caused the extinction of large groups of organisms at certain points in the past
-uniformitarianism:
-developed by Lyell
-the idea that geologic processes that have changed the shape of Earth's surface in the past continue to work in the same ways

Lamarck

-put forward a new idea to explain how evolution could happen (though it is no longer accepted)
-he thought that simple forms of life inevitably develop into more complex forms
-proposed that individuals could acquire traits during their lifetime as a result of experience or behavior, then pass on those traits to offspring
-his idea is called inheritance of acquired characteristics

natural selection

-a theory proposed by Darwin as the mechanism for descent with modification
-there was four main parts of Darwin's reasoning:
1. overproduction (more offspring are produced than can survive)
2. genetic variation (within a population, individuals have different traits)
3. struggle to survive (individuals compete for existence, and some variations improve an individual's chance to survive)
4. differential reproduction (through inheritance, successful adaptations will become more frequent in the population)

fitness

-a measure of an individual's hereditary contribution to the next generation
-"survival of the fittest" is a kind of fitness that is more than simply living a long time: a fit individual is one that has offspring that also live long enough to reproduce in a given environment

homologous structure

-anatomical structures that occur in different species and that originated by hereditary from a structure in the most recent common ancestor of the species
-have a related structure even if their functions differ between species

analogous structure

-have closely related functions but do not derive from the same ancestral structure
-ex: even though birds, bats, and moths have wings, they all have different structures

vestigial structures

-structures that seem to serve no function but resemble structures with functional roles in related organisms
-ex: the human tailbone resembles bones in an animal's tail, but the human one serves no purpose

divergent evolution

-a process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment
-ex: a wolf has diversified into many types of dogs

convergent evolution

-the process by which different species evolve similar traits
-ex: a bat (mammal) and bug (insect) can both fly, even though they are different species

artificial selection

-a process when a human breeder chooses individuals that will parent the next generation
-ex: dogs, horses, cats, birds, flower, vegetables

coevolution

-when two or more species have evolved adaptations to each other's influence
-ex: humans have used antibiotics to kill disease-causing bacteria, but populations of bacteria have evolved to resist the effects of antibiotics
-through coevolution, some species have evolved strategies to avoid being eaten, while the animals that eat them have evolved strategies to keep eating them

causes of genetic variation (5)

(1) mutation
(2) recombination (reshuffling of genes)
(3) random pairing of gametes
(4) environmental factors
(5) heredity

mutation in equilibrium

-the first requirement for genetic equilibrium is that the allele frequencies not change overall because of mutations
-can affect genetic equilibrium by producing totally new alleles for a trait
-many are harmful, though some have no effect
-because natural selection operates only on genes that are expressed, it is very slow to eliminate harmful recessive mutations

emigration

-the movement of individuals out of a population

immigration

-the movement of individuals into a population

gene flow

-the process of genes moving from one population to another
-can occur through various mechanisms, such as the migration of individuals or the dispersal of seeds or spores
-one of the requirements for genetic equilibrium is that there cannot be gene flow

random mating

-another requirement of genetic equilibrium is random mating, without regard to genetic makeup
-however, many species do not mate randomly

sexual selection

-a tendency for females to choose males they mate with based on certain traits
-extreme traits, such as heavy, brightly colored plumage, may give the female an indication of the quality of the male's genes or his fitness in the environment

genetic drift

-the phenomenon by which allele frequencies in a population change as a result of random events
-in small populations, the failure of even a single organism to reproduce can significantly disrupt the allele frequency of the population
-because it can result in significant changes, genetic drift is thought to be another possible mechanism for the evolution of new species
-so you would need large population sizes to get genetic equilibrium to prevent big changes

natural selection

-a requirement of genetic equilibrium is the absence of natural selection
-it means that some members of a population are more likely than others to survive and reproduce
-operates on variations of traits within a population
-when natural selection is at work over time, the distribution of traits in a population may change

stabilizing selection

-in this, individuals with the average form of a trait have the highest fitness
-it is a shift toward the center of the original bell curve in a graph

disruptive selection

-individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait
-there is a shift in both directions away from the center on a graph

directional selection

-individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait
-there is a shift in one direction only on a graph

allopatric speciation

-happens when species arise as a result of geographic isolation
-populations separated by a geographic barrier no longer experience gene flower between them
-so, gene pools of each separate population begin to differ due to genetic drift, mutations, and natural selection
-is more likely to occur in small populations because a smaller gene pool will be changed more significantly

sympatric speciation

-occurs when two subpopulations become reproductively isolated in the same geographic area
-ex: a population of insects might live on a single type of plant; if some of the individuals from this population began to live on another type of plant, they might no longer interbreed w/ the original; the two groups of insects would evolve independently

taxonomy

the science of describing, naming, and classifying organisms

Linnaeus

-Carolus Linnaeus devised a system of grouping organisms into hierarchical categories according to their form and structure
-each category represents a level of grouping
-his original system had seven levels, but there are eight now

levels of classification

-domain
-kingdom
-phylum (replaced by division in plants)
-class
-order
-family
-genus
-species
-King Phillip Chases Old Fat Girl Scouts

binomial nomenclature

-two-part name system for scientific names, consisting of genus and species
-both names are italicized
-the genus is capitalized, but the species is lowercased

cladistics

-a system of phylogenetic analysis that uses shared (a feature that all members of a group have) and derived (a feature that evolved only within the group under consideration) characteristics as the only criteria for grouping taxa
-developed by Willi Hennig

domains

-categories above the kingdom level
-only three: Archaea, Bacteria, and Eukarya
-not in Linnaeus's original system, but was added later by scientists

3 characteristics of ALL animals

-multicellular
-consumers
-eukaryotic cells

ectoderm

-the outer germ layer of an embryo
-forms the outer layer of the gastrula
-becomes the SKIN and NERVOUS SYSTEM

endoderm

-the inner germ layer of an embryo
-becomes the MUSCLES and BONES

mesoderm

-a third layer that forms between the endoderm and the ectoderm as development progresses in the embryo
-becomes the DIGESTIVE ORGANS

patterns of symmetry

-radial symmetry
-the parts are organization in a circle around an axis
-bilateral symmetry
-two similar halves on either side of a central plane
-asymmetry
-not displaying symmetry

cephalization

-the concentration of sensory and brain structures in the anterior (toward the head) region of the animal
-typically shown in bilaterally symmetrical animals
-as a cephalized animal moves through its environment, the anterior end precedes the rest of the body, sensing the environment

cleavage

-the series of cell divisions that occurs immediately following fertilization
-stages:
-steps 1., 2., 3.: the number of cells increases from 2 to 4 to 8 and so on
-step 4. it produces a mass of 16-64 cells
-step 5. the mass becomes a blastula
-during cleavage, mitotic divisions rapidly increase the number of cells, but the cells don't grow in size
-increases the surface area-to-volume ratio of each cell, which enhances gas exchange and other environmental interactions

blastula

-a hollow ball of cells
-happens in step 5 of cleavage
-the central cavity is called the blastocoel
-during gastrulation, the blastula collapses inward and the blastula is transformed into a gastrula

gastrulation

-the process of transforming the blastula into a multilayered embryo
-the cells at one end of the blastula moves inward
-gastrulation is marked by changes in the shape of cells and the way cells interact with each other

gastrula

a multilayered embryo

blastopore fate

-in the embryos of mollusks, arthropods, and annelids, the blastopore develops into a mouth, and a second opening forms at the other end, forming an anus (protostomes)
-in the embryos of echinoderms and chordates, the blastopore develops into an anus, and a second opening becomes the mouth (deuterostomes)

protostomes

-the blastopore develops into a mouth, and a second opening forms at the other end of the archenteron, forming an anus
-in embryos of mollusks, arthropods, and annelids
-means "first mouth"
-many undergo spiral cleavage

deuterostome

-the blastopore develops into an anus, and a second opening at the other end of the archenteron becomes the mouth
-in embryos of echinoderms and chordates
-means "second mouth"
-many undergo radial cleavage

acoelomate

-animals that don't have a body cavity
-the interior is solid
-the endodermic gut and the outer covering of the animal are connected by a solid tissue of mesoderm
-ex: flatworms

pseudocoelomate

-a cavity that is not completely lined by mesoderm
-in pseudocoelomates, mesoderm lines the fluid-filled body cavity, and the endodermic gut is suspended in this fluid
-ex: roundworms

coelomate

-a cavity completely lined by mesoderm
-in coelomates, mesoderm lines the body cavity and surrounds and supports the endodermic gut
-the mesoderm also forms the tissues of attachment for the organs located in the coelom, such as the liver and the lungs
-ex: mollusks, annelids, chordates, arthropods, and echinoderms

Phylum Porifera

made up of sponges

sessile

-when an animal attaches themselves firmly to a surface and doesn't move
-adult sponges are sessile

choanocyte

-flagellated cells that draw water into the sponge through numerous pores by beating their flagella
-lines the interior of the body wall cylinder of a sponge

osculum

-the opening at the top of the sponge
-the water that is pumped into the interior of the sponge leaves through here

spicules

-some sponges have skeletons consisting of these
-they are tiny, hard particles of calcium carbonate or silicon dioxide that are often shaped like spikes

filter feeding

-when the flagella of choanocytes beat, drawing water through the osculum, and the choanocytes trap plankton and other tiny organisms in their small, hair-like projections
-used in sponges because they cannot pursue food since they are sessile

amoebocytes

-cells that crawl within the body wall of a sponge (after receiving nutrients from the choanocytes) and deliver the nutrients to the rest of the body
-called amoebocyte because they resemble amoebas

sponge reproduction

-can reproduce asexually by forming small buds that break off and live separately
-they can also reproduce sexually, by releasing sperm into the water from one sponge and entering the pores of a second sponge
-are hermaphrodites

polyp

-a vase-shaped cnidarian
-specialized for a sessile existence

medusa

-bell-shaped cnidarian
-specialized for swimming

cnidarian cell layers

-there are two layers:
-an outer epidermis
-an inner gastrodermis
-between these layers is a jelly-like material called mesoglea

mesoglea

-a jelly-like material in between cell layers in a cnidarian

gastrovascular cavity

-a hollow gut in the center of a cnidarian
-has a single opening, or mouth, which is surrounded by tentacles

cnidocyte

-specialized cells used for defense and capturing prey
-in some cnidarians, the cnidocytes are concentrated in the epidermis, especially on the tentacles
-inside it is the organelle, the nemotocyst
-when an object brushes against the "trigger" on a cnidocyte, the nematocyst inside it pushes the filament out of the cell with great force

nematocyst

-a cnidocyte organelle with a long filament coiled up inside it
-when an object brushes against the "trigger" on a cnidocyte, the nematocyst inside it pushes the filament out of the cell with great force
-some nematocysts have filaments with sharp tips and spines that puncture the object and inject poison
-others have filaments that hold on to the object by wrapping around it

nerve net

-a scattered web of interconnected nerve cells that controls nervous responses in cnidarians
-in many cnidarians, the nerve net is distributed uniformly throughout the entire body
-there is no brain or similar structure that controls the rest of the nerve net
-it enables cnidarians to respond to specific stimuli in their environment

Class Hydrozoa

-most in class Hydrozoa live as colonial organisms
-ex: Portuguese man-of-war, hydra
-hydra can either move by floating in water or tumbling
-hydras generally reproduce asexually during warm weather and sexually in the fall

Class Scyphozoa

-"cup animals" which describes the medusa, the dominant form of the life cycle of this class
-known commonly as jellyfish
-move through pulsating motions of the cup
-the common jellyfish is a scyphozoan whose life cycle includes medusa and polyp forms

Class Anthozoa

-"flower animals"
-ex: sea anemones and corals
-sea anemones are polyps commonly found in coastal areas, where they attach themselves to rocks and other submerged objects
-anemones have symbiotic relationship with clownfish
-corals are polyps; when they die, their skeletons serve as the foundation for new polyps
-over thousands of years, they build coral reefs

Class Cubozoa

-"box jellies"
-have cube-shaped medusae
-a tentacle or group of tentacles is found at each corner of the "box"
-the cnidocytes of some can inflict severe pain, or death, among humans
-ex: sea wasp

reproduction in jellyfish

1. adult medusae release sperm and eggs into the water, where fertilization occurs
2. the resulting zygote divides many times to form a blastula
3. the blastula develops into a ciliated larva called a planula
4. the planula attaches to the ocean bottom
5. the planula becomes a polyp by developing a mouth and tentacles as the unattached end
6. the polyp grows and forms a stack of medusae
7. the medusae detach and develop into free-swimming jellyfish

Phylum Platyhelminthes

-ex: flatworms
-the classes are divided into Tuberllaria, Trematoda, Monogenea, and Cestoda

excretion in planaria

-eliminate excess water through a network of excretory tubules that run the length of the body
-each tubule is connected to several flame cells, which are so named because they enclose tufts of beating cilia that resemble candle flames
-the beating of cilia in flame cells draws in the excess water
-the water is then transported through the tubules and excreted from numerous pores scattered over the body surface

planaria reproduction

-planarians are hermaphrodites and can sexually reproduce by simultaneously fertilizing each other
-they can also reproduce sexually, through a process called fission
-fission is when the body constricts just behind the pharynx, and while the posterior part of the worm is attached to a solid surface, the anterior part moves forward until the worm splits in two
-planaria regenerate to produce 2 complete planaria

tapeworm anatomy

-tapeworms are surrounded by a tegument that protects them from their host's defenses
-at the anterior end is a knob-shaped organ called the scolex which has hooks and suckers that enable the worm to attach to its host
-a short neck connects the scolex with a long series of body sections called proglottids
-have no mouth, gastrovascular cavity, or other digestive organs
-absorb nutrients directly through their tegument

Phylum Nematoda

-they are pseudocoelomates
-ex: roundworms

Mollusca means...

-"soft body"

are Mollusks coelomates?

yes, they are coelomates

trochophore

-the larval stage of development in mollusks and annelids
-it is a free-swimming larva, propelled by cilia on the surface

visceral mass

-region that contains the heart and the organs of digestion, excretion, and reproduction
-located above the head-foot

mantle

-produces the shell
-covers the visceral mass
-the space between the mantle and visceral mass is the mantle cavity, which protects the gills

ganglia of mollusk

-paired clusters of nerve cells that make up the nervous system of a mollusk
-situated in the head-foot and visceral mass, and connected by two pairs of long nerve cords
-nerve cells in the ganglia...
-control the muscles for locomotion
-control the muscles for feeding
-process sensory information

radula

-a flexible, tonguelike strip of tissue covered with teeth that point backward
-has a variety of functions in different mollusks

Class Gastropoda

-examples:
-snail, slug, conch, abalone, nudibranchs
-undergo torsion during development
-"twisting"
-the visceral mass twists and the mantle cavity, gills, and anus is brought to the front of the animal
-because of this, a gastropod can withdraw its head when threatened
-have an open circulatory system

Class Bivalvia

-examples:
-clams, oysters, scallops
-their shell is divided into two halves connected by a hinge
-most are sessile
-lack a distinct head, but their nervous system has three pairs of ganglia, connected by nerve cords

Class Cephalopoda

-examples:
-octopus, squid, cuttlefish, chamber nautilus
-specialized for free-swimming, predatory existence
-the cephalopod brain, which is the largest of any invertebrate brain, is divided into several lobes and contains millions of nerve cells
-have a closed circulatory system
-also have separate sexes
-have pigment cells called chromatophores which can produce a sudden change in the animal's color

phylum Annelida

-means "little rings"
-bilaterally symmetrical, segmented worms
-have a true coelom, but it is divided into several compartments, which is an advantage

setae

-external bristles on most annelids
-earthworms:
-use their setae for movement
-it grips the ground as the longitudinal muscles contract
-Polychaetes:
-setae project from parapodia, some of which function in gas exchange
-has many setae to help it move
-leeches:
-have no setae

parapodia

fleshy protrusions that some annelids have

Class Oligochaeta

-means "few bristles"
-generally live in soil or fresh water and have no parapodia
-ex: earthworm

Class Polychaeta

-means "many bristles"
-have antennae and specialized mouthparts
-are also the only annelids with a trochophore stage
-most polychaetes live in marine habitats

Class Hirudinea

-ex: leeches
-leeches have no setae or parapodia
-at each end of a leech's body is a sucker that can attach to surfaces
-many are carnivores, but some are parasites

earthworm digestive tract

-food is sucked into the mouth by the muscular pharynx
-next, it goes to the esophagus (tube that soil is passed through)
-then moved into the temporary storage area called the crop
-the gizzard grinds the soil
-as the soil goes through the intestine, digested organic compounds and nutrients are absorbed by the blood
-undigested material goes out through the anus

circulation in earthworms

-have a closed circulatory system
-blood travels toward the posterior end through a ventral blood vessel then returns to the anterior end through a dorsal blood vessel
-five pairs of muscular tubes, the aortic arches, link the dorsal and ventral blood vessels
-contractions of the dorsal blood vessel and aortic arches force blood through the circulatory system

respiration in earthworms

-oxygen and carbon dioxide diffuse directly through the skin, which contains many small blood vessels
-BUT this can only happen if the skin is moist!
-therefore, earthworms avoid dry ground and extreme heat

excretion in earthworms

-eliminate cellular wastes and excess water through nephridia (like a kidney)
-each segment, except the first three and last one, contains a pair of nephridia
-as coelomic fluid passes through the nephridia, some of the water is reabsorbed by blood vessels
-remaining fluid/wastes dissolved in it are released from the body through pores on the ventral surface

nervous system in earthworms

-consists of a chain of ganglia connected by a ventral nerve cord
-they are cephalized and have a brain
-one of the main functions of the brain is to process information from sensory structures, which are concentrated at the anterior end

clitellum

-a thickened section of the body in earthworms
-when earthworms mate, they press their ventral surfaces together with the anterior ends pointing in opposite directions
-they are held together by their setae and by a film of mucus secreted by each worm's clitellum

Phylum Arthropoda

-segmented with jointed appendages
-their protection is in their exoskeleton
-have a high degree of cephalization
-have a compound eye
-open circulatory system
-go through the process of molting

compound eye

-eyes made of many individual light detectors, each with its own lens
-useful for:
-detecting movement
-direction
-NOT good at detecting images
-seen in arthropods

molting

-process of an arthropod shedding its exoskeleton and making a new one
-the cycle begins with the tissues of an arthropod swelling
-when the pressure inside the exoskeleton is strong, a hormone that triggers molting is produced
-the epidermis begins to make a new exoskeleton by using the digested material
-eventually, the outer layer of the old exoskeleton is shed, and a new, flexible one stretches to fit
-while the new exoskeleton is becoming hard, the animal is vulnerable to predators

chitin

-a tough polysaccharide
-makes up the middle layer (which provides the primary protection) of the exoskeleton of an arthropod

arthropods evolved how many years ago?

appeared 545 million years ago

phylogeny in arthropods

-very little is understood
-because all arthropods have a true coelom, an exoskeleton, and jointed appendages, biologists infer that all arthropods evolved from a common ancestor
-the order in which subgroups evolved are unclear

tagma

-a larger structure that is made of fused segments
-plural is tagmata
-the tagmata tend to be specialized for functions such as feeding, locomotion, and reproduction
-in arthropods, the cephalothorax consists of two tagmata

mandibles

a jaw-like major type of mouthpart

chelicerae

pincher-like major type of mouthpart

single defining feature of a crustacean

two pairs of antennae

crayfish order

Decapoda, which means "10 feet"

parts of the crayfish

-cephalothorax
-a major section of the body
-consists of two tagmata:
-the head
-the thorax, which has eight segments and is behind the head
-abdomen
-the tagma behind the cephalothorax
-divided into six segments
-antennae
-feelers that respond to touch and taste
-antennules
-serve as feelers sensitive to touch, taste, and balance
-mandibles
-jaw
-also used to catch/grasp food
-maxilla
-used for grasping food
-maxillaped
-used to manipulate food
-involved in respiration
-cheliped
-used for capturing food
-also used for defense
-walking legs
-used for movement on surfaces
-swimmerets
-create water currents
-function in reproduction

nauplius

-the free-swimming larva in many crustaceans
-has three pairs of appendages and a single eye in the middle of its head

respiration in crayfish

-have featherlike gills for respiration
-the gills extend from the base of each walking leg into a chamber under the carapace
-as the crayfish walks, its legs circulate water across its gills
-feathery branches on the posterior pair of maxillae also help direct water over the gills

excretion in crayfish

-excess water and wastes is eliminated by excretory organs called green glands
-the dilute fluid collected by the green glands leaves the body through a pore at the base of the antennae

nervous system in crayfish

-the brain consists of a pair of ganglia above the esophagus that receive nerve impulses from the eyes, antennules, and antennae
-two bundles of nerve fibers extend from the brain and pass around each side of esophagus to ganglion that controls mandibles, maxillae, and maxillipeds
-the ventral nerve cord runs posteriorly from this ganglion, connecting a series of ganglia that control the appendages and muscles in the segments of the thorax and abdomen

Subphylum Chelicerata

-examples:
-spiders, scorpions, mites, sea spiders, horseshoe crabs
-lack antennae
-have six pairs of appendages
-the first pair of appendages, chelicerae, are modified into pincers or fangs

spider respiration

-in some spiders, respiration occurs in the book lungs (paired sacs in the abdomen with many parallel folds that resemble the pages of a book)
-the folds in the book lung provide a large surface area for gas exchange
-other spiders have a system of tubes called tracheae that carry air directly to the tissues from openings in the exoskeleton, known as spiracles
-some spiders have both

arachnid body parts

-cephalothorax
-chelicerae (modified as fangs and used to inject venom into prey)
-pedipalps (handle food/prey, deposit sperm)
-four walking legs
-abdomen (no appendages)
-eight simple eyes
-produces silk threads using spinnerets
-respires through spiracles (like a pore) connected to book lungs or tracheae
-uses Malpighian tubules to excrete

spider eyes

-most have 8 simple eyes at front of cephalothorax
-each simple eye has a single lens

spinnerets

-composed of hundreds of microscopic tubes that connect to silk glands in the abdomen
-a protein-containing fluid produced in silk glands hardens into threads as it is secreted from spinnerets
-on the tip of the abdomen

spider excretion

-main excretory organs, called Malpighian tubules, are hollow projections of digestive tract that collect body fluids and wastes that carry them to intestine
-after most of the water is reabsorbed, the wastes leave the body in a nearly solid form with the feces
-thus, Malpighian tubules help spiders conserve water in earthly environments

sexual dimorphism in spiders

the female spider is usually bigger than the male

Class Diplopoda

-ex: millipedes
-rounded body
-four legs per segment (two pairs of legs per segment)
-eat decaying vegetation
-in Subphylum Myriapoda

Class Chilopoda

-ex: centipedes
-flat body
-one pair of joined legs per each body segment (except first and last two)
-eat bugs
-in Subphylum Myriapoda

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