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1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Page 1: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Define ‘homeostasis’

What things to animals do to maintain homeostasis?

Page 2: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Lecture 12 Outline (Ch. 40)

I. Animal Size/Shape and the Environment

II. Tissues

III. Feedback control and Heat Balance

IV. Bioenergetics and Energy Use

V. Lecture Concepts

Page 3: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Overview: Diverse Forms, Common Challenges

• Anatomy: study of biological form of an organism

• Physiology: study of biological functions of an organism

Page 4: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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(a) Tuna

(b) Penguin

(c) Seal

Physical Constraints on Animal Size and Shape

• Evolutionary convergence reflects different species’ adaptations to similar environmental challenge

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Exchange

0.15 mm

(a) Single cell

1.5 mm

(b) Two layers of cells

Exchange

Exchange

Mouth

Gastrovascularcavity

Animals sizes and shapes directly affect how they exchange energy and materials with surroundings

Exchange with the Environment

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0.5 cmNutrients

Digestivesystem

Lining of small intestine

MouthFood

External environment

Animalbody

CO2 O2

Circulatorysystem

Heart

Respiratorysystem

Cells

Interstitialfluid

Excretorysystem

Anus

Unabsorbedmatter (feces)

Metabolic waste products(nitrogenous waste)

Kidney tubules

10 µm

50 µ

m

Lung tissue

• More complex organisms have highly folded internal surfaces

Exchange with the Environment

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• Most animals are composed of specialized cells organized into tissues that have different functions

• Tissues make up organs, which together make up organ systems

Hierarchical Organization of Body Plans

Table 40.1

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• Tissues are classified into four main categories: epithelial, connective, muscle, and nervous

Tissue Structure and Function

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Epithelial Tissue

Cuboidalepithelium

Simplecolumnarepithelium

Pseudostratifiedciliatedcolumnarepithelium

Stratifiedsquamousepithelium

Simplesquamousepithelium

Note differences in cell shape and type of layering

Tissue Structure and Function

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Apical surface

Basal surfaceBasal lamina

40 µm

Tissue Structure and Function

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Connective Tissue

• Connective tissue mainly binds and supports other tissues

• It contains sparsely packed cells scattered throughout an extracellular matrix

• The matrix consists of fibers in a liquid, jellylike, or solid foundation

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Connective Tissue

Collagenous fiber

Looseconnectivetissue

Elastic fiber12

0 µ

m

Cartilage

Chondrocytes

10

0 µ

m

Chondroitinsulfate

Adiposetissue

Fat droplets

15

0 µ

m

White blood cells

55

µm

Plasma Red bloodcells

Blood

Nuclei

Fibrousconnectivetissue

30

µm

Osteon

Bone

Central canal

70

0 µ

mTissue Structure and Function

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Muscle Tissue

• Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals

• It is divided in the vertebrate body into three types:

– Skeletal muscle, or striated muscle, is responsible for voluntary movement

– Smooth muscle is responsible for involuntary body activities

– Cardiac muscle is responsible for contraction of the heart

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Muscle Tissue

50 µmSkeletalmuscle

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Smoothmuscle

Cardiac muscle

Nucleus

Musclefibers

25 µm

Nucleus Intercalateddisk

Tissue Structure and Function

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Nervous Tissue

• Nervous tissue senses stimuli and transmits signals throughout the animal

• Nervous tissue contains:– Neurons, or nerve cells, that transmit nerve impulses– Glial cells, or glia, that help nourish, insulate, and

replenish neurons

Page 16: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Glial cells

Nervous Tissue

15 µm

Dendrites

Cell body

Axon

Neuron

Axons

Blood vessel

40 µm

Tissue Structure and Function

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Self-Check

Tissue Category Tissues/Cells Included; Functions

Epithelial

Connective

Muscle

Nervous

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Feedback control loops maintain the internal environment in many animals

• Animals manage their internal environment by regulating or conforming to the external environment

Homeostasis

Stimulus:Perturbation/stress

Response/effector

Control center

Sensor/receptor

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Response:Heater turnedoff

Stimulus:Control center(thermostat)reads too hot

Roomtemperaturedecreases

Setpoint:20ºC

Roomtemperature

increases

Stimulus:Control center(thermostat)

reads too cold

Response:Heater turnedon

Feedback control loops maintain the internal environment in many animals

Page 20: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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Feedback control loops maintain the internal environment in many animals

• Thermoregulation: process by which animals maintain an internal temperature

(a) A walrus, an endotherm

(b) A lizard, an ectotherm

• Endothermic animals generate heat by metabolism (birds and mammals)

• Ectothermic animals gain heat from external sources (invertebrates, fishes, amphibians, and non-avian reptiles)

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Balancing Heat Loss and Gain

• Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation

Radiation Evaporation

Convection Conduction

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Epidermis

Dermis

Hypodermis

Adipose tissue

Blood vessels

Hair

Sweatpore

Muscle

Nerve

Sweatgland

Oil glandHair follicle

Balancing Heat Loss and Gain

• Balancing temperature usually involves the integumentary system

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• Five general adaptations help animals thermoregulate:

– Insulation– Circulatory adaptations– Cooling by evaporative heat

loss– Behavioral responses– Adjusting metabolic heat

production

Balancing Heat Loss and Gain

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• Bioenergetics is the overall flow and transformation of energy in an animal

• It determines how much food an animal needs and relates to an animal’s size, activity, and environment

Organic moleculesin foodExternal

environment

Animalbody Digestion and

absorption

Nutrient moleculesin body cells

Carbonskeletons

Cellularrespiration

ATP

Heat

Energy lostin feces

Energy lost innitrogenouswaste

Heat

Biosynthesis

Heat

Heat

Cellularwork

Energy Allocation and Use

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• Metabolic rate is the amount of energy an animal uses in a unit of time

Energy Use

Measured by determining the amount of oxygen consumed or carbon dioxide produced

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• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature

• Standard metabolic rate (SMR) is the metabolic rate of an ectotherm at rest at a specific temperature

• Ectotherms have much lower metabolic rates than endotherms of a comparable size

Energy Use

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Shrew

Harvest mouseMouse

Ground squirrel

Rat

Cat Dog

Sheep

Human

Horse

Elephant

Body mass (kg) (log scale)

BM

R (

L O

2/h

r) (

log

sc

ale

)

(a) Relationship of BMR to body size

10–3 10–210–2

10–1

10–1

1

1

10 102 103

10

102

103Energy Use

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10310210110–110–210–30

1

2

3

4

5

6

7

8

Body mass (kg) (log scale)

(b) Relationship of BMR per kilogram of body mass to body size

BM

R (

L O

2/h

r) (

per

kg

)Shrew

Harvest mouse

Mouse

Rat

Ground squirrel

Cat

Sheep

DogHuman

Horse

Elephant

Energy Use

Page 29: 1 Define ‘homeostasis’ What things to animals do to maintain homeostasis?

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An

nu

al e

ner

gy

exp

end

itu

re (

kcal

/hr)

60-kg female humanfrom temperate climate

800,000

Basal(standard)metabolism

ReproductionThermoregulation

Growth

Activity

340,000

4-kg male Adélie penguinfrom Antarctica (brooding)

4,000

0.025-kg female deer mousefrom temperateNorth America

8,000

4-kg female easternindigo snake

Endotherms Ectotherm

Energy Use

Different animals budget their energy differently.

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• Torpor is a physiological state in which activity is low and metabolism decreases – allows animals to save energy while avoiding difficult and dangerous conditions

• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity

Energy Use

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Additional metabolism that would benecessary to stay active in winterActual

metabolism

Arousals

Bodytemperature

Outsidetemperature Burrow

temperature

Met

abo

lic

rate

(kca

l p

er d

ay)

Tem

per

atu

re (

°C)

June August October December February April–15

–10

–5

0

5

15

10

25

20

35

30

0

100

200

Energy Use

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Lecture 12 concepts

- Distinguish among the following sets of terms: ectotherms and endotherms, positive and negative feedback; basal and standard metabolic rates; torpor and hibernation.

- Identify and describe the function of the following animal tissues: epithelial, connective tissue (six types), muscle tissue (three types), and nervous tissue (two types).

- Define metabolic rate and explain how it can be determined for animals

- Describe how an animals size affects its interaction with the environment, and metabolic rate.

- Discuss bioenergetics.

- Make a list of new vocabulary with definitions.