BIOL 117 Chapter 40: Chapter 40 Outline
Chapter 40
Overview- Diverse Forms, Common Challenges
● All animals must obtain oxygen and nutrients, fight off infection, and produce offspring.
40.1 Animal form and function are correlated at all levels of organization
● Evolution of Animal Size and Shape
○ Natural selection often results in similar adaptations when diverse organisms
face the same environmental challenge, such as overcoming drag during
swimming.
○ As body dimensions increase, thicker skeletons are required to maintain
adequate support for swimming
● Exchange with the Environment
○ Animals must exchange materials with their environment, and it occurs as
substances dissolved in an aqueous solution move across the plasma membrane
of each cell.
○ The opportunity for exchange depends on the number of cells in an organism’s
body. A single-celled organism, has a sufficient membrane surface area in
contact with its environment to carry out all necessary exchange.
○ In contrast, an animal is composed of many cells, each with its own plasma
membrane across which ex- change must occur.
○ A multicellular organization therefore works only if every cell has access to a
suitable aqueous environment, either inside or outside the animal’s body.
○ In humans, the internal exchange surfaces of the digestive, respiratory, and
circulatory systems each have an area more than 25 times that of the skin
○Interstitial Fluid- The spaces between cells that are filled with fluid in many
animals.
○ Internal body fluids link exchange surfaces to body cells
○ A complex body plan is especially advantageous for animals living on land,
where the external environment may be highly variable.
● Hierarchical Organization of Body Plans
○ Cells are organized into tissues, groups of cells with a similar appearance and a
common function
○ Different types of tissues are further organized into functional units called organs
○ Organ System- groups of organs that work together to provide an additional
level of organization and coordination
○ The specialized and complex organ systems of animals are built from a limited
set of cell and tissue types.
○ There are four main types of animal tissues: epithelial, connective, muscle, and
nervous.
● Coordination and Control
○ An animal’s tissues, organs, and organ systems must act in concert with one
another.
○ Coordinating activity across an animal’s body in this way requires communication
between different locations in the body.
○ In the endocrine system, signaling molecules released into the bloodstream by
endocrine cells reach all locations in the body.
○ In the nervous system, neurons transmit signals, called nerve impulses, between
specific locations in the body.
○ In each system, the type of pathway used is the same regardless of whether the
signal reaches across the length of the body or ends up just a few cell diameters
away.
○ Hormones- the signaling molecules broadcasted throughout the body by the
endocrine system
○ May have an effect on only one part of the body
○ For example, only cells of the thyroid gland have the receptor for
thyroid-stimulating hormone (TSH).
○ The effects of hormones are often long-lasting, however, because hormones
remain in the bloodstream for seconds, minutes, or even hours.
○ In the nervous system, signals are not broadcast throughout the entire body.
○ Instead, each nerve impulse travels to specific target cells along dedicated
communication lines consisting mainly of axons
■ Four types of cells can receive nerve impulses:
● other neurons
● muscle cells
● endocrine cells
● and exocrine cells.
■ Unlike the endocrine system, the nervous system conveys information by
the pathway the signal takes.
○ Nerve impulses travel along axons, sometimes over long distances, as changes
in voltage.
○ Two major communication systems of the body differ in signal type, transmission,
speed, and duration= they are adapted to different functions.
● SUMMARY
○ Physical laws constrain the evolution of an animal’s size and shape. These
constraints contribute to convergent evolution, the similar but independent
adaptations of different species to a common environmental challenge.
○ Each animal cell must have access to an aqueous environment. Simple
two-layered sacs and flat shapes maximize exposure to the surrounding medium.
More complex body plans have highly folded internal surfaces specialized for
exchanging materials.
○ In the hierarchical organization of animal bodies, groups of cells with a common
structure and function make up tissues. Different tissues make up organs, which
together make up organ systems. Animal tissues fall into four main groups, each
Document Summary
All animals must obtain oxygen and nutrients, fight off infection, and produce offspring. 40. 1 animal form and function are correlated at all levels of organization. Natural selection often results in similar adaptations when diverse organisms face the same environmental challenge, such as overcoming drag during swimming. As body dimensions increase, thicker skeletons are required to maintain adequate support for swimming. Animals must exchange materials with their environment, and it occurs as substances dissolved in an aqueous solution move across the plasma membrane of each cell. The opportunity for exchange depends on the number of cells in an organism"s body. A single-celled organism, has a sufficient membrane surface area in contact with its environment to carry out all necessary exchange. In contrast, an animal is composed of many cells, each with its own plasma membrane across which ex- change must occur.
