Biology 106 Lecture Topic # 21: Diversity- Animals

I. Animal Diversity

A. Characteristics of Animals:multicell. Euk, motile, heterotrophic by ingestion, develop from embryos, often exhibit complex behavior.

B. Diverse in form

C. Constructed in a common manner

1. Lack cell walls, relatively flexible

2. Cells generally organized into tissues (specialization)

a. groups of cells with structural and functional unity

b. further organization into organs

3. Movement - is the ____________________________________________.

a. move faster & more efficiently

4. Reproduce Sexually

a. nonmotile eggs

b. cells formed by meiosis function directly as gametes

c. adults & juveniles diploid

d. gametes only haploid cell = meiosis

II. Classification of Animals

III. At least 7 Major Evolutionary Advances in Animal Kingdom

Examine w/r two basic consistent Selective Forces:

1. Improved locomotion; 2. Diverse feeding habits

#1 Advance: Cell Specialization, Owing to envir. conditions that existed during animal prominence

a. oxygen atmosphere, b. mats of algae, c. floating zooplankton & phytoplankton

d. opportunity for "sit & wait" filtering lifestyles

Sponges (Phylum Porifera) = animals w/o tissues, - primarily marine

- possess choanocytes = specialized flagellated cells that line internal cavity

- possess epithelial layer of flattened cells, frequently contractile

- possess mesenchyme = intermediate layer of amoeboid cells

Filter feeders and large cells opened way for predators of larger organisms

Cnidarians - show further specialization w/ devel. of internal digestive cavity

ex.,

- digestive enzymes secreted into a primitive gut

- nerve cells organized into nets to coordinate muscle contraction

#2 Advance: Triploblasty

Ctenophores and Cnidarians areDiploblastic = ectoderm & endoderm

- Triploblasty adds mesoderm, cell lineages lead to different tissues and organs- further differentiation, ex.,

- An important advancement that was necessary for the next innovation because the mesoderm gives rise to major body muscles and interacts w/ other 2 layers to form complex sensory organs of the HEAD.

#3 Advance: Bilateral Symmetry, Important in basic body plan of an animal

- exhibit right and left halves, - more efficient locomotion

- allows for differential adaptations of various body parts, ex., sensory functions grouped an anterior (HEAD)

#4 Advance: Internal Body Cavity (Protects internal organs)

Three basic body plans:

A. Acoelomate = no body cavity other than digestive system- gut only internal cavity

- ex.,

- lack circulatory system,

- rely on diffusion,

- simple nervous system

- digestive system w/ only one opening

B. Pseudocoelomate = body cavity develops between mesoderm & endoderm

- ex.,

- pseudocoel serves as a hydrostatic skeleton against which muscles contract. - Fluid filled cavity increases mobility & allows larger sizes

- lack defined circulatory system

- digestive system w/ two openings

C. Coelomate = body cavity completely surrounded by mesoderm

- ex.,

- organs located in fluid filled cavity that resists pressure from muscles

- cavity may act as a circulatory system

- more efficient digestive system

- allows space for expansion of gonads & accumulation of gametes

Two Major Branches of Coelomates:

a) Protostomes

- ex.,

- mouth develops from blastospore

- exhibit several spiral cleavages in early embryo

- devel. fate of each cell fixed when that cell first appears =Determinate.

b) Deuterostomes

- ex.,

- anus develops from blastospore

- exhibit radial cleavage in early embryo

- commitment to cell differentiation occurs at late stage = Indeterminate

- 1st coelomate fossils include both protostomes & deuterostomes (630 mybp)

#5 Advance: Segmentation

- exhibited by annelids & arthropods

- adv., damage to one segment not fatal, since have duplication of organs

- more efficient locomotion due to increased flexibility

- segmentation in adv. animals not always evident, but may be present in embryos

- ex.,

#6 Advance: Tagmosis = Reduction of segmentation by fusion of adjacent segments into a functional unit

Tagmosis & segmentation were such key innovations that evolved two separate times in

1) annelids & arthropods - primary segmentation in coelom

2) chordates - primary segmentation seen in muscles

#7 Advance: Jointed Appendages

-ex, arthropods "hand-in-hand" development w/ rigid exoskeleton

- associated w/ hard external body coverings

- Exoskeleton must be shed to grow larger, A ________________.

- Internal skeleton against which muscles work avoids disadv. of exoskeleton

- facilitates feeding & movement

- can be modified into antennae, mouthparts, legs

- Chordata most highly developed internal skeleton.

- Subphylum vertebrata

*skull for brain

*organs: kidneys, liver, heart, endocrine glands

*circulatory and excretory functions markedly different from other animals

IV. Invasion of Land

Same problems faced by fungi & plants, ____________________ &________________

Adaptations to gravity: - strong skeleton, - increased body size

Adaptations to desiccation - water resistant body covering

- increased body size - specialized kidney for conc. urine

- loss of aquatic larval stage - increase reproductive structure complexity