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Ch. 40 – animal form and function
Overview
Animals inhabit almost every part of the biosphere (earth, water, and air – basically the planet)
All animals face a similar set of problems (food, shelter, water, space)
When you look at and study animals, you can see that form and function are closely related, which is what helps them address their problems (food, shelter, water, space)
Physical laws and the environment constrain animal size and shape Physical laws and the need
to exchange materials with the environment place limits on the range of animal forms (like size)
The ability to perform certain actions depends on an animal’s shape and size
Evolutionary convergence reflects different species’ adaptations to a similar environmental challenge (for example, most animals that live in water all have certain features in common)
Exchange with the environment An animal’s size and shape directly
affect how it exchanges energy and materials with its surroundings
Exchange occurs as substances dissolved are transported across the cells’ plasma membranes
EXAMPLES: A single-celled protist living in water
has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm
Multicellular organisms with a sac body plan (like the hydra or jellyfish) have body walls that are only two cells thick, facilitating diffusion of materials
A tapeworm is very thin, so as it sits in the intestinal juices of it’s host it can easily diffuse nutrients
More complex organisms have highly folded internal surfaces for exchanging materials (like the intestines).
*This is an important tie-in to past concepts, like respiration, surface area, and the cell membrane
Diffusion
Mouth
Diffusion
Two cell layersSingle cell
Diffusion
Gastrovascularcavity
Digestivesystem
Circulatorysystem
Excretorysystem
Interstitialfluid
Cells
Nutrients
Heart
Animalbody
Respiratorysystem
Bloo
d
CO2FoodMouth
External environment
O2
50 µ
m
A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM).
10 µm
Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM).
The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM).
Unabsorbedmatter (feces)
Metabolic wasteproducts (urine)
Anus
0.5 cm
Animal Form and the Levels of Organization The levels of organization
are: Cell-tissue-organ-organ
system-organism Most animals are
composed of specialized cells (eukaryotic) organized into tissues
Different tissues have different structures that are suited to their functions
Tissues are classified into four main categories: epithelial, connective, muscle, and nervous
Tissues Epithelial tissue covers the outside of
the body and lines the organs and cavities within the body (first line of defense against foreign invaders)
Connective tissue mainly binds and supports other tissues (Ligaments are an example)
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 (voluntary actions,
striated, attached to bone), Cardiac (found in the walls of the
heart) smooth (found in hollow organ
cavities like the stomach , bladder, and uterus; involuntary actions)
Nervous tissue senses stimuli and transmits signals throughout the animal Brain, spinal cord
Organ Systems
These are groups of organs working together to perform a specific function
Organ systems carry out the major body functions of most animals
11 organ systems are found in the human body
How many organ systems and their functions can you name?
Organ Systems
• Digestive System: mouth … anus
• Circulatory System: heart, blood vessels, blood
• Respiratory System: lungs, trachea, other breathing tubes
• Immune and Lymphatic System: marrow, lymph nodes, spleen, WBC
• Excretory System: kidneys, ureters, bladder, urethra
• Endocrine System: hormone-secreting glands
• Reproductive System: ovaries, testes, etc.
• Nervous System: brain, spinal cord, nerves
• Integumentary System: skin and its derivatives
• Skeletal System: bones, tendons, ligaments, cartilage
• Muscular System: skeletal muscles
Using Energy in Food
All organisms require chemical energy for growth, repair, physiological processes, regulation, and reproduction (you are what you eat)
Bioenergetics (the flow of energy through an animal – how living things make use of free energy), limits behavior, growth, and reproduction
It determines how much food an animal needs
Studying bioenergetics tells us about an animal’s adaptations
Bioenergetics cont.
We are constantly burning ATP (free-energy), and if we don’t do that, we die
Remember the laws of thermodynamics? (1st – law of conservation of energy; we can convert energy, but not destroy it. 2nd – with each reaction, we release some heat, which increases entropy)
Energy sources and allocation (how to get it) Animals harvest chemical
energy from food (heterotrophs)
Energy-containing molecules from food are usually used to make ATP, which powers cellular work (through cellular respiration)
After the needs of staying alive are met, remaining food molecules can be used in biosynthesis (creating chemical compounds in a living organism – basically making more cells)
Metabolism Metabolism is how
quickly an organism consumes energy
Metabolic rates are affected by many factors, including whether an animal is an endotherm (create their own heat) or ectotherm (use heat from their surroundings), size, and activity levels
Relationship between metabolism and size larger organisms have low
metabolisms compared to a smaller organism
Basically the smaller organism has a harder time maintaining homeostasis because it loses a lot of heat
*we’ll talk about ectotherms and endotherms later in these notes (during thermoregulation)
Use of energy is partitioned to activity, homeostasis, growth, and reproduction
Homeostasis
The internal environment of vertebrates is called the interstitial fluid and is very different from the external environment
Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes
This is our ability to maintain a stable internal environment regardless of outside conditions
Homeostasis – positive and negative feedback loops Humans use feedback loops to
maintain homeostasis (in our house we use a thermostat)
All loops have a receptor (the thermostat, or what receives the signal), and effectors (what’s affected by a change in a stimulus – the thermostat will turn off or on, depending on the temp.)
Overview – positive and negative feedback loops in homeostasis A negative feedback
loop brings you closer to a set target point (temperature regulation is an example)
A positive feedback loop amplifies or moves you away from a set target point (fruit ripening is an example)
Alterations are mistakes in the feedback loops (diabetes is an example – problems sensing insulin)
4 Important Homeostatic Mechanisms (that use feedback loops) Thermoregulate (Maintain
temp)– controlled by hypothalamus
Blood glucose (gives us the fuel for our cells) – controlled by the pancreas
Blood calcium (used for our nerves, muscles) – controlled by thyroid and parathyroid
Osmolarity (concentration of the blood – remember hypotonic and hypertonic?) – controlled by hypothalamus and pituitary
We’ll talk about the first two feedback loops in the next several slides, as well as a couple of others that are on your standards
Feedback loops – positive feedback Positive feedback: this is when you
overshoot your target – produce too much of something
Used when we want something to happen quickly – it usually doesn’t go on for a long period of time.
Examples:
If you wanted fruit on a tree to ripen (and they do this to attract animals that will spread the seeds), the plants communicate by releasing ethylene (remember your plant hormones?), which causes the fruit to ripen at the same time. This causes amplification, so as the fruit ripens, more and more fruit ripens
Childbirth – the pressure of the babies head on the cervix causes contractions, which puts more pressure on the cervix, which causes more contractions (until the baby is born)
Feedback Loops cont. – blood glucose (when things go wrong) Examples of negative
feedback – glucose levels and diabetes
Your pancreas helps put digestive enzymes into your small intestine to help break down food, but they also help regulate glucose levels.
They have two types of cells – beta and alpha – whose major jobs are to sense the glucose level in your blood.
Feedback Loops cont. – blood glucose (when things go wrong) If we have a lot of blood glucose, the
beta cells sense that and it causes our body to release some calcium and insulin (so when the blood glucose is high, insulin is released from the pancreas, spreads through the body, and it tells our cells to absorb the glucose. (It also tells our liver to store it as glycogen).
This causes our blood glucose to go down.
When those levels go down, the body stops producing insulin, and the alpha cells tell the body to start producing glucagon, which increases the blood glucose level.
When you increase glucose, there is an increase in insulin – when glucose levels fall, insulin levels fall
Feedback Loops cont. – blood glucose (when things go wrong) In a diabetic (type I) the beta
cells don’t work. That means when the blood glucose goes up, there’s nothing there to tell the body to secrete insulin, so the glucose continues to go up. This increases blood pressure, nausea, blindness, and death.
Type II diabetics (consume too much glucose in your life, not enough exercise) – your body stops recognizing insulin and therefore stops taking it in. They have to take insulin shots throughout the day (usually around mealtimes)
Thermoregulation – aiding in homeostasis Thermoregulation
is the process by which animals maintain an internal temperature within a tolerable range
Thermoregulation - overview There are a few basic ways to
transfer heat: Conduction- (direct contact
(you actually touch a flame Convection – movement of
heat through air and fluids (heater)
Radiation – transfer of heat through empty space (sun to the earth)
Respiration – though metabolism we can generate heat
(the book also mentions evaporation, which is the removal of heat from the surface of a liquid that’s turning to gas – like when you sweat)
Thermoregulation cont. Life has evolved a couple of different
strategies to interact with heat:
1. Ectotherm (heat from outside) – they derive their temp from their surroundings.
Advantages – don’t need to burn up energy to create energy
Disadvantage – if it’s really cold, your body processes slow down too
*tend to have a lower metabolism
In general, ectotherms tolerate greater variation in internal temperature than endotherms
2. Endotherms – generate heat inside of them (metabolism)
Advantages – internal temp. is always the same
Disadvantage – constantly need to eat to maintain temp.
*tend to have a higher metabolism
Balancing Heat Loss and Gain In thermoregulation,
physiological and behavioral adjustments balance heat loss and gain
Five general adaptations help animals thermoregulate: Insulation Circulatory adaptations Cooling by evaporative
heat loss Behavioral responses Adjusting metabolic
heat production
thermoregulation cont. -(negative feedback )
Humans (and all endotherms) use a negative feedback loop to maintain a constant body temp (approx. 98 degrees F)
If you get too hot, your hypothalamus (in your brain) senses the change, and causes you to sweat , and blood is carried to the surface of your skin through vasodilatation, which cools your blood through convection. You also sweat, which cools through evaporation
If you get too cold, then you start to get goose bumps (which causes hair to stand up and contracts your skin), blood gets pulled closer into your body, called vasoconstriction (decreasing convection), and you can shiver to create heat.
Insulation
Insulation is a major thermoregulatory adaptation in mammals and birds
It reduces heat flow between an animal and its environment
Examples are skin, feathers, fur, and blubber
In mammals, the integumentary system acts as insulating material
Circulatory Adaptations
Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin
In vasodilatation, blood flow in the skin increases, facilitating heat loss
In vasoconstriction, blood flow in the skin decreases, lowering heat loss
Circulatory Adaptations cont Many marine mammals and birds have an arrangement of blood vessels called a countercurrent heat exchanger
Countercurrent heat exchangers are important for reducing heat loss
Arterial blood leaves the bird’s core at a warm body temperature, while venous (returning) blood in the bird’s foot is quite cool.
As cold blood runs up the leg from the foot and passes by the arteries, it picks up most of the heat from the arteries via conductance.
As it travels, the blood flowing down is cooled, and the blood flowing up is warmed.
Thus, by the time arterial blood reaches the foot, it is cool and does not lose too much heat in the cold water, and venous blood reaching the core has already been warmed, helping maintain core heat.
Cooling by Evaporative Heat Loss Many types of
animals lose heat through evaporation of water in sweat
Panting augments the cooling effect in birds and many mammals
Bathing moistens the skin, helping to cool an animal down
Behavioral Responses
Both endotherms and ectotherms use behavioral responses to control body temperature
Some terrestrial invertebrates have postures that minimize or maximize (or minimize) absorption of solar heat
Acclimatization
In acclimatization, many animals adjust to a new range of environmental temperatures over a period of days or weeks
Acclimatization may involve cellular adjustments or (as in birds and mammals) adjustments of insulation and metabolic heat production
Torpor and Energy Conservation Torpor is a physiological
state in which activity is low and metabolism decreases
Torpor enables 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
Estivation, or summer torpor, enables animals to survive long periods of high temperatures and scarce water supplies
Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns