Vertebrate Natural History
Lecture 7 - Functioning in an Aquatic Realm
1st Lecture Exam -- September 27th
FITB, Definition, short answer
Introduction
Living in water demands unique adaptations. - Density: Water >800 times as dense as air. o Supports body weight; weight-bearing skeleton not necessary o Can grow larger, little effect of gravity on body structure. o Aquatic animals tend to be significantly larger than land animals. Viscosity -- Water 18 times as viscous as air. o Viscosity -- measure of how a fluid flow across a surface. Induces drag on the animal's body. The viscosity of water compared to running on land - less tired when swimming. More streamlines body shapes to reduce the amount of drag in the aquatic environment. Why important? Flow-thru ventilation more efficient (water going across the gills) Increase in efficiency; breathing at the same time, allowing the water to flow through the gills easier. o More later. o Oxygen content -- at best, water 4 times lower than air; often 20 times (or more!) lower in terms of oxygen content. - Flow-thru ventilation more efficient. As a result, bc of the low oxygen availability, need to be more efficient in oxygen uptake. Heat capacity and conductivity; specific heat of water 3,400 times that of air. Water conducts heat 24 times as fast as air. o Specific Heat -- energy needed to produce 1 degree Celsius in temperature in 1 g fluid. Water tends to be more stable from day to night when it comes to temperature. Animals can adapt to different temperature zones within aquatic habitats. Water temperature stable at given depth. : Advantages : Disadvantages o Water is an Electrical Conductor -- Electrical conductivity is useful for detection in changes in the environment. Generalized skeleton of bony fishes: o Not robust structure.
o Decidedly not weight-bearing. Vertebrae and ribs predominate. Main support Ribs/spines thin; flexible (need flexibility to contort the body) Facilitate swimming motions o Fins supported by "rays' Operculae; jaws Respiration; feeding -Bring water into the mouth and is forced across the gills = pumping system Breathing under water o O/CO2 exchanged via gills for most. o Generalized design. Opercular cavities Operculae (plural); operculum (singular) Gill arches -- support the overall gill; "backbone" for the gills. Gill filaments - coming off gill arch; feather-like projections; in between each are gill slits, where water flows through. Gill slits -- water flows through. Water moves the opposite direction Countercurrent exchange maximizes uptake of O and release of CO2. o Blood flows one way and water flows the other and passively moves through Secondary Lamellae. o Oxygen has small concentration -- there should be a strong diffusion gradient. Oxygen is going to passively diffuse in the secondary lamellae. The blood picks up oxygen and acts like a sponge and interacts with freshwater (highest concentration of oxygen). Moving in opposite directions = always picking up oxygen. Types of Ventilation: o Forceful (flow-thru) -- pumping water into mouth and out over the gills. Example: most fishes Ti