An overview Invertebrates

Response (1.Centralization) A simple nerve net has concentrations of nerves at specific areas of the animal This centralized format allows for quick movement of nervous signals to help coordinate response Examples: jellyfish, flatworms

Response (2.Cephalization) Animals with bilateral symmetry have concentrations of nerves at the anterior end of body Cephalization increases as animals increase in complexity Simple cephalization results in a ganglia or clump of nerves; more complex cephalization results in an organized brain

Response (3.Specialization) The more complex the animals, the more highly specialized its sense organs!

Internal Transport Ways that materials are moved around the body Oxygen & nutrients need to be brought to cells Wastes need to be carried away

1. Diffusion Materials move directly through the tissues of the animals Move from areas of high to low concentration Examples: echinoderms (starfish) & flatworms

Closed System Network of blood vessels Diffusion of materials occurs b/w blood & cells through blood vessels Blood usually doesn’t directly contact tissues Examples: annelids, chordates

Open System No blood vessels Tissues “bathed” in blood Body sinuses collect blood HEART pumps blood in BOTH open & closed systems! Examples: arthropods & molluscs

Respiration Goals are to supply oxygen and remove carbon dioxide from body cells ALL systems require: - system for increasing surface area for gas exchange - need a moist gas exchange surface

Respiration across the skin via diffusion (ex. Hydra)

Gills exchange gases with surrounding water (ex. Crayfish)

Tracheal tubes (grasshopper) have evolved for breathing air

Reproduction & Development Some reproduce ASEXUALLY by fragmentation or budding Benefits: - produce offspring quickly - produce many offspring Not so good stuff: - genetically identical to parent (not good for diversity)

Most reproduce SEXUALLY - new combinations of genes - separate gametes (males produce sperm and females produce eggs) - some are hermaphrodites (both genders at once)

External Fertilization In less complex animals Gametes are released into the surroundings (aquatic) Large numbers of gametes at one time

Internal Fertilization In more complex animals Mostly land animals Usually one egg fertilized, although many sperm released at one time Sperm deposited directly in female reproductive tract

Movement Almost all animals use muscles for movement These muscles work with a firm skeletal system that provides support There are 3 types: exoskeleton, hydrostatic & endoskeleton

EXOSKELETON Examples: molluscs & arthropods Hard coating (made of chitin or calcium carbonate) covers internal organs

2. HYDROSTATIC Examples: cnidarians & flatworms No hard structures (bone or chitin) Muscles supported by water filled cavity

3. ENDOSKELETON Examples: echinoderms & vertebrates Frame of support inside body Muscles attach to skeletal structure

Feeding- Three Evolutionary Trends 1.How food is broken down 2.# of openings of digestive space 3.Specialized regions of digestive tract Examples Simple Animals Intracellular digestion Single opening None  gastrovascular cavity digests & absorbs nutrients Flatworms Complex Animals Extracellular digestion Mouth takes in food  anus expels waste Specialized regions as food moves in 1 direction through body Molluscs & arthropods

Excretion Regulates the levels of water in the body & get rid of nitrogenous waste Formed during the process of cellular respiration

THREE types of wastes produced… 1.Ammonia (NH3) 2.Urea 3.Uric Acid Relationship to environment Highly toxic; very soluble in H2O Soluble in H2O Less soluble in H2O but not as toxic as ammonia How they get rid of it Diffuses through body tissues into surrounding water Concentrated urea forms urine with excess H2O Excreted as a thick paste Animals that excrete this waste Aquatic invertebrates Terrestrial animals Insects (terrestrial)

Flame cells in flatworms

Nephridia in earthworms

Malpighian tubules (grasshoppers) Pre-urine is formed in the tubules Wastes such as urea diffuse through walls Ions such as sodium & potassium are moved actively Water follows