NOTES FOR BIOLOGY 1002

SECTIONS 004, 005, 006

Spring 2006

DR. STEVEN POMARICO

CHAPTER 28

HOW PLANT AND ANIMALS WORK

In biology structure is correlated which function

Because of this two import fields of study within biology are anatomy and physiology.

Anatomy - is the study of an organism's form or structure.

Physiology - is the study of an organism's function.

Levels of structural organization are present and help shape the division of labor.

          Tissues are specialized cells with a common structure and function that are                                 grouped together.

          Organs are centers of bodily function, which are usually made up of different                      tissues.

          Organ systems are groups of two or more organs that function together to                      perform a common task (e.g., digestion, gas exchange, reproduction)

Growth Versus Development

Growth is the increase in the number, size, and volume of the cells of a multicelled organism.

Development refers to the successive stages in the formation of specialized tissues, organs, and organ systems.

The internal environment

Plant and animal cells must be bathed in a fluid that provides nutrients and carries away wastes.

The internal environment—extracellular fluids—provides this stable environment.

Homeostasis describes the relative constancy of the internal environment even when external conditions change.

The Nature of Adaptation

Short-term vs long-term

Short-term adaptations, such as an individual plant's stunted growth on a windy plain, last only as long a the individual does.

Long-term adaptations have some heritable aspect that improves the odds for surviving and reproducing.

Mechanisms of homeostasis in animals

Homeostatic control mechanisms require three components:

          Sensory receptors - detect specific changes in the environment.

          Integrators - (brain and spinal cord) act to direct impulses to the place where

                                 a response can be made.

          Effectors - (muscles and glands) perform the appropriate response.

This “maintenance of an internal environment” is a dynamic process which require continual regulation (and energy)

How is this done?

          Negative feedback

          Positive feedback

Negative feedback - a change in one direction causes a series of events in the other direction to counteract the change.

Biological example: maintenance of body temperature at 98.6 ^oF. (37 ^oC.)

Real life example: Your apartment's thermostat.

Drop in temp turns on heat, until it reaches set point, then stops.

There are many similar negative feedbacks in the body (water loss, blood sugar)

Positive feedback - initial change in one direction sets off a series of events that intensifies a change in that same direction.

Biological examples: Childbirth.

Real life example: classic snowball effect.

Childbirth

          1) Early in labor, uterus starts to contract,

          2) This starts to force baby's head into cervix,

          3) This stretches the cervix and causes the receptors in the cervix to                               signal uterus to contract further.

          4) Usually once the process begins it continues until the baby is pushed out.

Plants and homeostasis.

          While plants do not have centralized mechanisms to maintain the internal environment, they do exhibit homeostasis.

Walling off threats - compartmentalization

Some plant respond to attack by walling off threats to their internal environment.

Compartmentalization isolates the threat from the remainder of the plant.

          Many plants show a variety of mechanisms to regulate water loss.

Communication among cells, tissues, and organs require - signal reception, transduction, and response.

In large multicelled organisms, cells in one tissue need to signal cells that are often quite a distance away.

In general a signaling molecule binds to a receptor initiating a transduction of the signal into a form that operate inside the cell to cause a functional response.

Communication in the plant body

Hormones are the main signals for cell plant communication.

Expression of specific genes in some cells can change a hormone's level in plant tissues.

          -The ABC model for flowering describes three genes that are the master

                      switches for floral development—sepals, petals, and other structures.

Communication in the animal body

Neurons of the vertebrate nervous system constitute a communication system.

Hormones also provide an important method for communication in animals.

Recurring challenges to survival

          Gas Exchange

                     Animals take in oxygen and give off carbon dioxide; plants do mostly the

                                 reverse.

                     Diffusion down a concentration gradient drives these movements.

Requirements for internal transport

          The surface-to-volume ratio of an organism must be kept to receive the

                      nutrients and discharge the wastes.

          Substances must be transported within the organism also by vascular tissue:

                     - xylem and phloem in plants

                     - arteries and veins in animals.

Maintaining a solute-water balance

          Plants and animals constantly gain and lose water and solutes.

          Substances may move by passive diffusion into and out of the body but

                     active transport is required to pump specific substances against

                                 the gradient.