Chapter 3: Ecological and Evolutionary Principles Chapter 4: Form and Function: The chemical and physical environment ©Jeffrey S. Levinton 2001.

Chapter 3: Ecological and Evolutionary Principles

Chapter 4: Form and Function:

The chemical and physical environment

©Jeffrey S. Levinton 2001

The Ecological Hierarchy

• Biosphere: entire set of living organisms and non-living on the Earth.

• Ecosystem: includes many communities, both abiotic and biotic factors

• Community: made of several populations all living in the same place.

• Population: group of individuals made of same species.

• Individual: is an organism that is independent of other individuals.

Ecological Terms

Habitat: place an organism lives (like an address). Habitat is species specific.

Niche: function of organism in its habitat or environment (the organism’s job)

How do organisms interact with each other?

How do marine organisms interact with their environment?

Interactions Between Individuals(Table 3.1)

• +- Territoriality

• +- Predation

• + - Parasitism

• ++ Mutualism

• + 0 Commensalism

• +- or -- Competition

Territoriality in marine fishes:

Above: damsel fish defend territories of coral or algal mats that they farm.

Below: Clown fish protect and defend anemones that are their homes.

Parasitism

• Parasites evolve to reduce damage to host

• Commonly involve complex life cycles with more than one host

• Parasites may invade specific tissues, such as reproductive tissue of the host

Invasion of the parasitic barnacle Sacculina into the body of a crab

defecation

Complex life cycle found in a trematode parasite living in several marine animal hosts

Definitivehost

2ndintermediate

hosts

1st intermediatehost

defecation

predation

Cercaria

Encystedmetacercaria

Egg

Miracidium

Adultworm

Sporocyst

Redia

Mutualism: Cleaner wrasse removes ectoparasites from a number of species of fish that visit localized “cleaning stations” on a coral reef. Fish (b) is a mimic species that actually attacks fish that would normally be a “client” of the cleaner wrasse.

(a)

(b)

Cleaning stations occur in shallow water environments and many types of organisms use them.

Commensalism

Commensal crab and fish live in this burrow of Urechis caupo (a worm species)

How do marine animals interact with their environment? (abiotic factors)

•Temperature

•Salinity

•Oxygen

•Light

Measures of organism’s response include:

•Behavioral

•Physiological

•biochemical

Temperature

• Temperature variation is common in marine environment:

Latitudinal temperature gradient can be very pronounced (Jordon’s Rule)

Seasonal temperature change commonShort term changes (e.g. weather changes, tidal

changes)• Tolerance to temperature is an important factor

in the distribution of marine organisms• Temperature affects growth and reproduction

Temperature for homeotherms

• Heat loss - problem for homeotherms who maintain high body temperatures

Insulation - used by many vertebrates (blubber in whales, feathers in birds)

Countercurrent heat exchange - circulating venous and arterial blood in opposite directions while vessels are in contact to reduce heat loss

Temperature

Countercurrent heat exchange -Heating

Chamber37°C

27°C

28 °C 30 °C 32 °C 34 °C 36 °C

29 °C 31 °C 33 °C 35 °C 37 °C

Example of countercurrent heat retention

Temperature

Countercurrent heat exchange in dolphin limb - artery is surrounded by veinlets, which return heat

veinlets

Temperature

Poikilotherms - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature

Temperature

Met

abol

ic r

ate

Stabilization of metabolismover wide range of temperature

Temperature

• Freezing - a problem in winter in some environments and in high latitudes where sea ice forms, can destroy cells

Some fish have glycoproteins, which function as antifreeze

Example: Antarctic fish genus, Trematomus, live in water temps close to –1.9 C throughtout the year. These fish die if water temps exceed 6 C!

Antarctic Sea Urchin that produces chemicals to use very little energy (extremely low metabolic rates)

Salinity 1

• Salinity change affects organisms because of the processes of diffusion and osmosis

Salinity

• Example of osmosis problem - animal with a certain cellular salt content is placed in water with lower salinity: water will enter animal if it is permeable - cell volume will increase, creating stress

• (many marine inverts are permeable)

Salinity • Experiment - Place sipunculid worm

Golfingia gouldii in diluted seawater. At first volume increases of worm, but then worm excretes salts, regulating volume back

1 2Time (hours)

5

0

% B

ody

volu

me

chan

ge

Salinity 7

• Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations

• Problem - diffusion makes it difficult to regulate concentration of physiologically important ions such as calcium, sodium, potassium

Salinity

• Most marine organisms have ionic concentrations of cell constituents similar to seawater (see table 4.1)

• Marine organisms such as the Atlantic eel (Anguilla rostrata) can live in both freshwater and saltwater, however most have very narrow tolerance ranges of salinity.

Salinity 11

• Bony fishes - have overall salt concentrations of body fluids of 1/3 strength of regular seawater. Creates continual osmotic problem of water loss

Fish must drink continuouslyGills actively secrete saltsSharks employ urea to maintain osmotic balance

Salinity 12

• Bony fishes - osmotic regulationWater exchange

Solute exchange

Drinking

Drinking(seawater

containing ions)

Osmotic lossthrough gills

Na+,Cl-

(gill secretion)

Urine

Mg2+, SO42-

Oxygen 1• Most marine organisms require oxygen for

manufacture of necessary reserves of ATP, energy source in cells

• Some habitats are low on oxygen - Low tide for many intertidal animalsWithin sediment - often anoxic pore waterOxygen minimum layers in water column -

where organic matter accumulates at some depths

Oxygen • Oxygen uptake mechanisms:Animals only a few millimeters thick rely upon

diffusion for oxygen uptakeLarger animals use feathery gills with high

surface area to absorb oxygen; mammals have lungs with enormous surface areas to take up oxygen

Larger animals have circulatory systems that circulate oxygen to needy tissues. Many have oxygen-carrying blood pigments.

How do marine animals deal with low levels of Oxygen??

1. Decrease activity and therefore O2 consumption (intertidal crabs)

2. Switch to breathing air: examples include some crabs and mussels (Mytilus californianus consumes O2 at the same rate in air as water)

3. Use metabolic pathways that do not require O2

4. Alter blood pigments to carry more O2

5. Behavioral response to leave the environment.

This species of mussel opens when it is exposed to air and breathes through its valve.

Light

• Many animals detect light with aid of a simple layer of sensory cells, but many species have complex eyes with focusing mechanisms

Allows detection of prey, predators

Aids in navigation (some animals may use land masses or stars to aid in navigation of long migrations)

Light • Eyes of animals:

Pinhole camera Lens Curved, reflective Nautilus Fish Scallop

Scallops and oysters have the ability to detect light and even see images with reflective sensory organs.

Light

• Bioluminescence - light manufactures by organisms - using specialized light organs, sometimes with the aid of symbiotic bioluminescent bacteria

Functions to confuse predators or attract matesPerhaps other as yet undiscovered functions