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What defines something as living?
o Cells
o Metabolism
o Evolution
o Reproduction
o Contains genetic information
Nucleic acids synthesize proteins
o How life may have arose
§ Enclosure by membrane which created an internal environment that
allowed for microorganism specialization
Prokaryotes: bacteria and archaea
Eukaryotes: plants and animals
o Cellular specialization
o Internal membranes
Aerobic metabolism vs anaerobic metabolism = with oxygen vs without oxygen
A genome is the sum total of all the DNA in all the cells of an organism
DNA is long sequences of 4 nucleotides that contain genetic information
Genes are specific segments of DNA that encode information the cell uses to create
amino acids and form them into proteins which govern the chemical reactions within the
cells
All cells of the same organism contain the same genome but have different functions
Mutations can be spontaneous or be influenced by outside factors
Most mutations are either harmful or have no effect
A population is a group of individuals of the same species that interact with one another
o Evolution acts on populations, not individuals
o Mutations give rise to genetic changes
Any population displays variation
An adaptation is any structural, physiological, or behavioral change that enhances an
organism’s chances of survival
Sexual selection and genetic drift also change the allele frequencies of a population
A phylogeny is the history of evolutionary relationships
o HYPOTHESIS
o Each branching point is called a node and represents where lineages diverged
§ Speciation events
o The common ancestor is at the root
A taxon is a species or a group of species
o If it consists of an ancestor and all its descendants then it is a clade
§ Monophyletic
Two species that are each other’s closest relatives are called sister species
o Two closest related clades are sister clades
A homologous trait is any feature shared by two or more species who inherited it from a
common ancestor
A trait that was present in the ancestor of the group is an ancestral trait
A derived trait is a trait that an animal has that its descendant did not have
A synapomorphy is a shared derived trait that defines the group

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Convergent evolution is when two species share a trait but not from a common ancestor
and they derived it separately
Evolutionary reversal is when a character reverts back to an ancestral trait
The group of interest is the ingroup
o The outgroup is a comparison
The principle of parsimony is that the simplest explanation is the accepted one unless
evidence forces us to be more complicated
Polyphyletic groups do not include a common ancestor
Paraphyletic groups include the common ancestor but not all of its descendants
What characteristics distinguish the animals?
o Multicellularity
o Heterotrophic metabolism
o Internal digestion
o Movement and nervous system
Developmental Patterns
o Early cell divisions of an embryo are known as cleavage
§ Patterns are influenced by the configuration of the acellular, nutritive yolk
that nourishes the developing embryo
• Radial cleavage is the ancestral condition for animals other than
sponges
o Cells divide in an even pattern
• Spiral cleavage is a complicated permutation of radial cleavage
and is found among many lophotrochozoans
o Earthworms and clams
• Idiosyncratic cleavage is neither radial nor spiral in organization
o Most Ecdysozoans except early branches (insects and
nematodes)
o Diploblastic animals have embryos with two cell layers
§ Outer ectoderm and inner endoderm
• Ctenophores, placozoans, and cnidarians
§ Ancestral condition
o Triploblastic animals have embryos with 3 cell layers
§ Mesoderm lies between ectoderm and endoderm
§ Existence of three embryonic cell layers is a synapomorphy for triploblasts
o Gastrulation is when cells form a hollow ball one cell thick and indents to form a
cup shaped structure
§ The indentation is the blastopore
• In protostomes the blastopore develops into the mouth
• In deuterostomes the blastopore develops into the anus
o Bilaterians are protostomes and deuterostomes
What are the features of an animal body plan?
o Symmetry
o Structure of the body cavity (or lack thereof)
o Segmentation
o External appendages
o Nervous system

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Animal symmetry
o Spherical symmetry is when body parts radiate out from a central point with an
infinite number of symmetrical planes
§ Unicellular protists
o Radial symmetry is when body parts are arranged around one main axis at the
body’s center
§ Ctenophores, cnidarians, echinoderms
§ Some are sessile and some drift others move slowly but well in any
direction
o Bilateral symmetry is when there is one plane upon which symmetry occurs
§ Mirror image at midline of body
§ Bilateral symmetry is strongly correlated with cephalization
• Cephalization is when sensory organs and nervous tissues are
concentrated at the anterior end of the animal
Structure of body cavities
o Triploblastic animals can be separated into 3 categories
§ Acoelomates lack enclose, fluid-filled body cavities; instead, the space
between the endoderm and ectoderm is filled with mesenchyme
• These animals typically move by beating cilia
• Flatworms
§ Pseudocoelomates have a body cavity called a pseudocoel that is a fluidfilled space between the mesoderm and endoderm
• Internal organs are suspended in the pseudocoel
• Pseudocoel is only lined by mesoderm (muscles) on the outside;
there is no inner layer of mesoderm around the organs
§ Coelomates have a body cavity that develops within the mesoderm
• Coelom is lined with tissue called peritoneum which also
surrounds internal organs
• Coelomates have better control over the movement of its fluids
than pseudocoelomates
o The structure of an animal’s body cavity influences the way in which it can move
§ Body cavities of many animals function as a hydrostatic skeleton
• Fluids are relatively incompressible so when muscles around the
cavity contract, fluids shift to another part of the cavity
• If body tissues around cavity are flexible, fluids squeezed out of
the region can expand another region
Segmentation facilitates specialization of different body regions and allows animals to
control their movement more precisely
o Muscles of each individual segment can move that segment separately from the
others
Appendages are used for sensing the environment, moving, catching prey, and
reproduction
Cnidarians and ctenophores have diffuse nervous systems called nerve nets
Bilaterians have complex central nervous systems
Sponges and placozoans completely lack a nervous system
How do animals get their food?

Filter feeders strain small organisms from their environment
Herbivores eat plants
§ Often manage to not kill them
§ Do not need to expend energy
§ Plants can be difficult to digest
• Herbivores have long complex guts
o Predators capture and eat other animals
§ Sensitive sensory organs
o Parasites live in or on much larger organisms from which they obtain energy and
food
o Detritivores feed on dead organic material
How do life cycles differ among animals?
o Many feature specialized life stages
§ Direct development is when the offspring looks like a miniature version
of the adults
§ Most species’ newborns differ from the mature adult
• Larvae is an immature form
• Metamorphosis is a dramatic change that the species goes through
between its larval and adult stages
§ Often the different stages are specialized for different things
• One for feeding and one for reproduction
• Increases the efficiency with which the animal performs that
activity
o Most animal life cycles have at least one dispersal stage in which the organism
moves away from the parent or the existing population
§ Sessile adults typically disperse as eggs
• Sessile marine animals tend to discharge their eggs
o Many animals have a radially symmetric larval stage and are known as
trochophores and have a bilaterally symmetric mature stage called a nauplius
o Motile adults disperse when they are mature
o In order to survive, parasites must overcome their host’s defenses
§ They or their offspring must disperse to new hosts while the current host is
still living because they die when their host dies
• Many parasites have intermediate life stages with different hosts
and life cycles
Asexual reproduction without fission leads to the formation of colonies composed of
many physiologically integrated individuals
o Not a single organism but a colony of homogeneous clonal copies
§ In some colonies they all function alike while in others they become
specialized for different functions as different types of cells do
No life cycle can maximize all benefits so in order to improve one activity it must reduce
its performance in another like a trade off
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Homeostasis = a narrow range of stable physical and biochemical conditions under
which the body functions optimally
o Cells exist within an internal environment of extracellular matrix
§ Interstitial fluid bathes every cell in the body
• Provides nutrition

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Organs
Organs are always made of epithelial tissue and usually all 4 types
§ Epithelial tissue protects the body and its compartments and controls
what goes in and out of the body
• Skin
• Secrete hormones, milk, mucus, sweat, digestive enzymes
• Provide information for the nervous system
§ Muscle tissues generate force and movement
• Skeletal muscle is attached to bone for locomotion and other body
movements
• Cardiac muscle is responsible for pumping blood and makes up
the heart
• Smooth muscle makes up the inside of hollow organs
§ Connective tissue cells are generally dispersed in the extracellular matrix
that they make themselves
• Strength, resistant to stretch, structural, shape
• Cartilage and bone provide support
• Blood cells dispersed in plasma
• Adipose is fat cells that are a major source of stored energy
§ Neural tissue processes information
• Neurons encode and conduct information through electrical and
chemical signals that are received by target cells
• Glia provide support functions for neurons and can send chemical
signals
How does temperature affect living systems?
o Cells can only function over a narrow range of temperatures
§ Lower temp for most cells is 0 celsius and upper is 40-45 celsius
o Q10 is a measure of temperature sensitivity
§ =1 if the reaction is not temperature sensitive
• Reaction rate doubles as temperature goes up by 10 celsius
Endotherms produce more heat because their cells are less efficient at using energy
o Na+ ions are constantly diffusing into the cells and K+ ions are constantly
diffusing out of cells which means they expend more energy and release more
heat
Ectotherms can use behavior to maintain a fairly stable temperature
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Gets rid of waste
Protects from harsh conditions
Cells are specialized for maintaining certain aspects of the internal environment
§ Allows for multicellular animals to be larger, thicker, and more complex
Set point is compared with feedback which sends error signal to regulatory
systems and then control systems



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