chapter 20 - unifying concepts of animal structure and function

why is an animal’s form not a perfect design?

why is an animal’s form not a perfect design?

natural selection can only act on what is already there

• mechanisms by which existing structures arise from previous structures (evolutionary connection)

  • structures are going to be restricted physically due to its evolution

  • ex. giraffe’s long laryngeal nerve

anatomy

study of form of an organism’s structure

physiology

study of function of those structures

emergent properties

novel properties that were not present at the preceding level of the hierarchy of life

• arise as a result of the structural and functional organization of each level’s component parts and the interaction among those parts

example of emergent properties

• a single cell

  • muscle cell - to contract, and strands of proteins that perform that function are precisely aligned (each cell is branched and connected to other cells in a way that ensures coordinated contractions of the heart)

• tissue (an integrated group of similar cells that performs a similar function)

  • the cells are specialized, and their structure enables them to perform a specific task

    • muscle tissue - cellular structure allows for coordinated contraction

• organ (made up of two or more types of tissues that together performs a specific task)

  • heart - made up of muscle, nervous, epithelial, and connective tissue (heart’s ability to pump blood is resulted from the coordinated contraction)

• organ system (multiple organs that together performs one or more vital body functions)

  • circulatory system - made up of the heart, blood and blood vessels, arteries, veins, and capillaries

• organism (each organ system is specialized for certain tasks and all functioning together as an integrated, coordinated unit)

  • giraffe - systems cannot function without other systems and takes the coordination of several organ systems and emergent properties for life

tissues

an integrated group of similar cells that perform a common function and combine to form organs

4 main categories of tissues

1. epithelial tissue

2. connective tissue

3. muscle tissue

4. nervous tissue

extracellular matrix

one side of an epithelium is attached to a dense mat consisting of fibrous proteins and sticky polysaccharides

apical surface

one side that faces the outside of an organ or the inside of a tube or passageway

epithelial tissue

sheets of closely packed cells that cover the body surface and line the internal organs and cavities

• tightly knit cells form a protective barrier and, in some cases, a surface for exchange with the fluid or air on the other side

  *named according to

  • the number of cell layers they have

  • shape of cells on their apical surface

    *the structure of each type fits its function

simple epithelium

single layer of cells

stratified epithelium

multiple layers

squamous

flat cells (like fried eggs)

cuboidal

cubed cells (like dice)

• has large amounts of cytoplasm (absorbtion)

columnar

column-shaped cells (like bricks on the end)

• has large amounts of cytoplasm (absorbtion)

simple squamous epithelium

thin and leaky

• suitable for exchanging materials by diffusion (lines capillaries and air sacs of lungs)

simple cuboidal epithelium

tube in kidney, found in thyroid and salivary glands

simple columnar epithelium

lines intestines where it absorbs nutrients

stratified squamous epithelium

lines the esophagus, outer skin, mouth

• regenerates rapidly

• new cells move to apical surface as old cells die off

connective tissue

consist of a sparse population of cells scattered throughout a matrix

• binds and supports other tissues

matrix

consists of a web of fibers embedded in a liquid, jelly, or solid

loose connective tissue

binds epithelia to underlying tissues and holds organs in place

• matrix is a loose weave of fibers in a watery fluid

fibrous connective tissue

forms tendons (muscles to bone) and ligaments (bones to joints)

• matrix of densely packed collagen fibers (maximizes its strength)

adipose tissue

stores fat in large, closely packed adipose cells

• sparse matrix of loose fibers and fluid

cartilage

forms a string but flexible skeletal material (surrounds ends of bones; making it shock-absorbant)

• matrix consists of collagen fibers embedded in a rubbery material

bone

provides shape and support for body (contains living cells — grows as you grow and mends when broken)

• matrix of collagen fivers embedded in a hard mineral substance made of calcium, magnesium, and phosphate (makes bone strong and not brittle)

blood

transports substances throughout the body (functions differently)

• extensive extracellular matrix is a liquid called plasma (water, salts, dissolved protiens)

  • suspended in plasma are red blood cells, white blood cells (fights against infections), and platelets (for clotting)

muscle tissue

the most abundant tissue in nearly all animals

• functions in movement

  • consists of long cells called muscle fibers (contains many molecules of contractive proteins)

skeletal muscle

attached to bones by tendons and is responsive for voluntary movements of the body

• arrangement of contractive units along the length of skeletal muscle fibers gives the cell a striped or striated appearance

cardiac muscle

forms the contractive tissue of the heart (involuntary control)

• is striated but branched, interconnecting at specialized junctions that rapidly relay the signal to contract cell to cell during a heart beat

smooth muscle

involuntary body activities and found in the walls of the digestive trait, arteries, and other internal organs

• has a lack of striations (hence the name) and contract slowly than skeletal muscle but can sustain contractions for longer periods of time

nervous tissue

forms a communication network by sensing stimuli and rapidly transmitting information

• found in the brain and spinal cord, and nerves that transmits signals throughout the body

neuron (nerve cell)

structural and functional unit of nervous tissue

• unquiely specialized to conduct electrical nerve impulses

  • dendrites — receives nerve impulses from other neurons (looks like roots or branches)

  • axons — transmits signals (looks like pathways)

  • cell body — necleus and orgenelles (center of neuron)

organ

made up of tissues

• represents a higher level of structure than the tissues composing it and perform functions none of the individual tissues can carry out alone (emerge from coordinated interactions of tissues)

• each tissue in the organ performs a specific function and can be organized into layers in some organs

the small intestine

• lined by a columnar epithelium which includes connective tissues that contain blood vessels, and has two layers of smooth muscle that helps propel food (surrounded by another layer of connective tissue and epithelial tiddye)

  • the inner surface has many finger-like projections that increase the surface area for absorbing (villi and micro-villi)

organ transplants

• hard to come by (lists are based by emergence and proximity)

• compatibility is a major issue too

  • bio engineers are seeking ways to repair or replace damaged tissues or organs by 3-D printing

3-D printing organs and tissues

to create a layer of cells to resemble the structure of tissues and organs

• however, they lack the correctly organized nerves, blood vessels, and other tissue and structures that would make them viable and functional in human bodies

scaffold

inner framework

• integrity of the tissue or organ

  • ex. connective tissue matrix of a heart

• new tissues and organs are being grown on a scaffold of connective tissue from donated organs

  • seeded with stem cells

stem cells

unspecialized cells that contain the genetic information to become specialized cells of the tissue or organ

organ systems

made up of organs

• work together to perform life functions

• the ability to carry out life’s functions is a result of the emergent properties stemming from the organization, interaction, and coordination of all the body’s organ systems working together

circulatory system

delivers oxygen and nutrients to body cells and transports carbon dioxide to the lungs and metabolic wastes to the kidneys

• heart, blood vessels

respiratory system

exchanges gases with the environment, supplying blood with oxygen and disposing of carbon dioxide

• nasal cavity, larynx, trachea, lungs, pharynx, bronchus

integumentary system

protects against physical injury, infection, excessive heat or cold, and drying out

• skin, hair, nails

skeletal system

supports the body, protect organs like the brain and lungs, and provides the framework for muscle movement

• bones, cartilage

muscular system

moves body, maintains posture, and produces heat

• skeletal muscles

urinary system

removes waste products from the blood and excretes urine while also regulating the chemical makeup, pH, and water balance of the blood

• kidneys, ureter, urinary bladder, urethra

digestive system

ingests and digests food, absorbs nutrients, and eliminates undigested materials

• mouth, esophagus, liver, stomach, small and large intestines, anus

endocrine system

secretes hormones that regulates body activities, thus maintaining an internal steady state called homeostasis

• hypothalamus, pituitary gland, thyroid gland, parathyroid gland, thymus, adrenal gland, pancreas, testis (male), ovary (female)

lymphatic system

returns excess body fluid to the circulatory system and functions as part of the immune system

• lymph nodes, thymus, spleen, appendix, bone marrow, lymphatic vessels

immune system

defends against infections and cancer

• lymph nodes, thymus, spleen, appendix, bone marrow, lymphatic vessels

nervous system

coordinates body activities by detecting stimuli, integrating information, and directing responses

• brain, sense organs, spinal cord, nerves

reproductive system

produces gametes and sex hormones (female system supports a developing embryo and produces milk)

• female: oviduct, ovary, uterus, vagina

• male: seminal vesicles, prostate gland, vas deferens, penis, urethra, testis

skin

consists of two layers

1. epidermis

2. dermis

epidermis

a stratified squamous epithelium with many layers of flat cells

• rapid cell division at the base of the epidermis served to replenish skin cells

  • fills with a protein keratin and releases oils

dermis

the inner layer of skin which consists of a fairly dense connective tissue with many elastic and collagen fibers (thinning of this layer results in wrinkled, sagging skin in older people)

• contains hair follicles, oil, sweat glands, muscles, nerves, and blood vessels

hypodermis

layer of adipose tissue beneath the skin

• site where vaccines and drugs are injected

vitamin D

required for absorbing calcium

folic acid

vitamin vital for fetal development

skin pigmentation and melanin

• northern areas have lighter skinned people to get enough levels of both vitamins

• southern areas have darker skinned people to avoid sunlight degrading folic acid while getting a healthy level of vitamin D

hair

flexible shaft of flexible, keratin-filled dead cells, which were produced by a hair follicle

• oil glands lubricate the hair, condition the surrounding skin, and inhabit the growth of bacteria

• wrapped in nerve endings

• insulation of land mammals

  • muscles is responsible for raising hair (goose-bumps)

nails

protective coverings composed of keratin

well-designed experiments

examining one variable at a time, including randomized controls, and controlling for bias in data interpretation

control groups

individuals who were not treated but used for comparison

• without it, we do not know the effects of that one particular variable (examining on one variable — ex. laser therapy)

  • should control all aspects and factors that could influence that controlled variable

    *to determine the effectiveness and affects of that variable

open system

organisms which exchanges matter and energy with its surroundings

• ex. humans take in water, food, and oxygen, and in exchange, they dispose of carbon dioxide, urinate, defecate, sweat, and radiate heat

  *key idea: surface area to volume ratio

external exchange

body cells exchange materials directly with the environment

• simple organisms (each cell in the body is close to the external environment — cells in small and flat organisms)

  • flattening (thin, flat body plan)

  • ex. parasitic tapeworm

internal exchange

an extensively branched or folded surface is a evolutionary adaptation that provides efficient exchange with the environment

• increasing surface area to volume ratio

• complex animals have specialized internal structures that increase surface area (act as exchange surfaces)

folding

creation of multiple layers or projections in tissues or organs to maximize the surface area relative to the volume

• folded surfaces are internal protected by the integumentary system (25x larger surface area than skin in humans)

branching

the formation of multiple, interconnected pathways or structures in biological systems that enhance the distribution and exchange of materials

interstitial fluid

body cells are bathed in this fluid

• this is where exchange takes place

  • direct exchange does not occur between blood and cells of tissues/organs but through this fluid

why do animals regulate their internal environment?

conditions often fluctuate widely in the external envrionemnt, by homeostatic mechanisms regulate internal conditions (smaller changes in an animal’s internal envrionment)

external envrionment

surrounds the animal

internal environment

where cells actually live

• the interstitial fluid that fills the paces around cells

  • body maintains salt & water balance and body temperature (temperature has to be in a range in which the body and proteins can function properly for life)

homeostatis

a steady state (dynamic)

• birds and mammals have control systems that keep body temperatures -and other factors - within a narrow range, despite large changes in the external environment

negative feedback

any control mechanism that reduces or reverses a change in the internal environment (bring back to the set point) — homeostasis depends on negative feedback

• ex. regulating levels of glucose and temperature

positive feedback

any control mechanism that amplifies a change (bring away from set point)

• ex. forming blood clots, producing contractions to push a baby out

hypothalamus

part of brain that regulates activities such as food intake, sleep, heart rate, hormone levels, and body temperature (maintains homeostasis)

• responds to variations from the set point by switching on and off mechanisms