Complexity and Diversity in Animal Biology

Levels of complexity in Kingdom Animalia

Protoplasmic level, cellular level, cell-tissue level, tissue-organ level, organ-system level.

Diploblastic organisms

Displaying only ectoderm and endoderm, no mesoderm, examples include cnidarians and ctenophores.

Triploblastic organisms

Displaying all three germ layers; all animal phyla more complex than the cnidarians.

Coelom

A coelomate has a second body cavity surrounded by mesoderm.

Pseudocoel

A pseudocoelomate has a second body cavity formed from blastocoel, not surrounded by mesoderm.

Acoelomate

An acoelomate has no body cavity other than the digestive tract.

Functional importance of coeloms and pseudocoeloms

They help maintain internal organ development and movement, transport nutrients and waste, and protect internal organs.

Metamerism (segmentation)

The serial division of the body into functional segments.

Advantages of metamerism

Each segment may develop a more complete set of adult organ systems, damage to any one segment may not be fatal, and locomotion is more effective.

Asymmetry

No plane through that can be divided into mirror image halves.

Radial symmetry

Body divided into similar halves by more than 2 planes passing through the longitudinal axis.

Bilateral symmetry

Organisms can be divided along a sagittal plane into two mirror image halves.

Cephalization

The differentiation of a head region with a concentration of nervous tissue and sense organs.

Extracellular digestion

Digestion that occurs outside of cells.

Intracellular digestion

Digestion that occurs within cells.

Complete digestive tract

A digestive tract with two openings, mouth and anus.

Incomplete digestive tract

A digestive tract with only one opening.

Fertilization

The process begins with the fertilization of an egg to form a zygote.

Cleavage

The early division of the zygote into multiple cells.

Gastrulation

The blastula becomes a 2-layered stage called a gastrula.

Neurulation

The neural plate folds to form the neural tube.

Types of cleavage

Includes meroblastic (incomplete cleavage) and holoblastic (complete cleavage).

Meroblastic cleavage

Incomplete cleavage where types include discoidal and superficial.

Holoblastic cleavage

Complete cleavage, can be isolecithal or mesolecithal.

Embryonic germ layers

The layers that develop into various structures and tissues in the embryo.

Archenteron formation

The invagination of the embryo at the blastopore forms the archenteron, which develops into the gut.

Formation of the coelom

In most bilaterally symmetric animals, the blastocoel fills with mesoderm to form a coelom.

Formation of the pseudocoel

In some animals, the mesoderm lines the outer edge of the blastocoel, forming a pseudocoelom.

Mesoderm

Lines the outer edge of the blastocoel, forming a pseudocoelom.

Protostome

Blastopore forms the mouth; includes animals that molt, some with a crest of tentacles, and some with a trochophore.

Deuterostome

Blastopore forms the anus; includes phyla Echinodermata, hemichordate, and chordata.

Tissue

Many cells integrated together with extracellular materials, such as collagen.

Epithelial Tissue

Derived from all germ layers of the embryo: ectoderm, mesoderm, and endoderm; provides physical protection, controls permeability, and provides sensation.

Connective Tissue

Derived from mesoderm; establishes the framework of the body, transports fluids, protects organs, supports other tissues, stores energy, and defends the body from microorganisms.

Muscle Tissue

Derived from mesoderm; responsible for external (locomotion/posture) and internal (digestion/circulation) movements.

Nervous Tissue

Derived from ectoderm; neurons transmit electrical signals, neuroglia cells support neural tissue, specialized for communication.

Circulatory System

Exchanges materials with the external environment, controls chemical balance, regulates body temperature, distributes hormones, and defends against foreign invaders.

Cardiovascular System

Involves heartbeat and carrying blood towards and away from the heart.

Respiratory System

Facilitates exchange of gases with the external environment, in conjunction with the circulatory system if present.

Digestive System

Breaks down food so that it can be absorbed and distributed.

Integumentary System

Acts as a barrier to pathogens, prevents mechanical or chemical damage, prevents water loss or gain, regulates body temperature, and provides sensory information.

Skeletal System

Supports the body, protects internal organs, and facilitates locomotion.

Excretory System

Eliminates nitrogenous waste products of metabolism and maintains the balance of water and solutes.

Nervous System

Processes sensory input and coordinates adaptive motor output, responding to external and internal stimuli.

Reproductive System

Asexual reproduction involves production of genetically identical offspring by a single parent; sexual reproduction involves production of genetically distinct offspring through genetic recombination.

Aquatic Respiratory Adaptation

Aquatic organisms use gills for respiration.

Terrestrial Respiratory Adaptation

Terrestrial organisms use lungs for respiration.

Aquatic Locomotion Adaptation

Aquatic organisms use fins for locomotion.

Terrestrial Locomotion Adaptation

Terrestrial organisms use limbs for locomotion.

Aquatic Sensory Adaptation

Aquatic organisms have specialized vision/senses.

Terrestrial Sensory Adaptation

Terrestrial organisms have enhanced vision/senses.

Aquatic Reproductive Adaptation

Aquatic organisms commonly use external fertilization.

Terrestrial Reproductive Adaptation

Terrestrial organisms commonly use internal fertilization.

Freshwater Water Balance

Freshwater organisms produce large amounts of dilute urine.

Marine Water Balance

Marine organisms produce small amounts of concentrated urine.

Freshwater Drinking Adaptation

Freshwater organisms drink minimally and absorb water through skin and gills.

Marine Drinking Adaptation

Marine organisms drink large quantities of water.

Ecology

The study of how living organisms interact with each other and their physical environment.

Ecosystem

A community of living organisms interacting with each other and their physical environment.

Community

A group of interacting organisms living in the same area.

Niche

Comprised of the ways that an organism utilizes resources and relates to its environment.

Fundamental Niche

The entire niche that an organism may theoretically occupy.

Realized Niche

The actual niche that the organism is able to occupy due to competition.

Competition

Describes the interaction that occurs when two organisms attempt to use the same resource, the consequence of niche overlap.

Principle of Competitive Exclusion

If two species are competing for a resource, the species that uses the resource more efficiently will eventually eliminate the other locally.

Resource Partitioning

Occurs when two or more species effectively divide up a resource, creating multiple niches.

Predation

Consuming of one organism by another.

Herbivory

The type of predation where the prey is a plant.

Keystone Species

Predators that reduce competition and increase community diversity.

Coevolution

The reciprocal adaptation that occurs between two species that are exerting significant selective pressure on each other.

Crypsis

When prey animals avoid predation by making themselves inconspicuous, blending in with their surrounding colors.

Aposematic Coloration

When prey animals use toxins to protect themselves against predator species and advertise with bright and toxic-looking colors.

Batesian Mimicry

When a palatable species resembles a poisonous one; there may also be nonvisual cues, such as olfaction, involved.

Mullerian Mimicry

When several unrelated, but protected, species come to resemble one another.

Symbiosis

A close and often long term interaction between two or more species.

Commensalism

Symbiotic relationship where one benefits and the other is unaffected, such as barnacles on a whale.

Parasitism

Symbiotic relationship where one benefits and the other is harmed, such as a tick on a dog.

Mutualism

Symbiotic relationship where both species benefit, such as a bee on a flower.

Population

A group of individuals of one species that occur in a particular region.

Population Size

The number of individuals in a population.

Population Density

The number of individuals found in a given area.

Population Dispersion

The spatial distribution of individuals within the population's range.

Population Growth

The change in the size of the population over time.

Exponential Growth Model

Shown in density independent models and defined by dN/dT= rN.

Logistic Growth Model

Shown in density dependent models and defined by dN/dT= rN(1-N/K).

R-selected Species

Defined based upon the rates that individuals are added to and subtracted from the population.

K-selected Species

The maximum number of individuals of a species that an ecosystem can support.

Survivorship Curve

A graph that represents the number of individuals in a population that survive to different ages.

Type 1 survivorship curve

Highest mortality for the oldest individuals.

Type 2 survivorship curve

Relatively the same mortality risk for all ages.

Type 3 survivorship curve

Highest mortality for the youngest individuals.

Ethology

The modern study of behavior, focused on innate, stereotyped behavior, studies behavior in its natural context and tries to understand its evolution.

Comparative psychology

Learning and the plasticity of behavior, natural context is viewed as irrelevant.

Behavioral ecology

The study of behavioral adaptation, links particular behaviors to particular environments/habitats.

Kittiwakes

Parents unable to recognize offspring, offspring are sedentary, no mobbing behavior.

Herring gulls

Parents able to recognize offspring 3 days after hatching, offspring move, mobbing behavior.

Territoriality

An area that is defended by one organism against other individuals, usually other members of the same species.

Mating system

Includes all of the different aspects of its reproduction, important characteristics include the number of mates and the amount of parental care provided by each sex.

Monogamy

One male mates with one female.

Polygyny

One male mates with multiple females.