UNIT 3ECOSYSTEMSTRATEGIES

3.1 SPECIALIST AND GENERALIST SPECIES

The way species utilize their niches can be broadly grouped as generalists or specialists.

1. The Giant Panda is an example of a specialist specie. It has a narrow niche with no predators except man.

2. The advantage of specialist species is that competition is reduced.

3. However, when food and habitat are limited, survival is threatened due to lack of adaptability.

4. Only about 800 Pandas are alive in the wild and 220 are in zoos. They are more closely related to raccoons than to bears.

5. The Panda’s habitat is western China where human population is soaring. It has become endangered because:

• loss of habitat - people are encroaching

• specialized diet – Pandas feed only on bamboo and need to spend most of the day eating up to 1/3 of its body weight.

• Bamboo has a natural tendency to die back and grow slowly.

• low birth rate - one cub every other year; at birth the baby is blind, without fur, and weighs only 5 oz.

6. Mothers must care for their young for 2 years - assuming the mother survives.

• finicky mating habits - Pandas are usually solitary, but during courting the males are very possessive.

Adults weigh about 250 lbs.

7. The American Alligator is an example of a generalist specie that also has no predators except man.8. It became endangered simply from hunting.

9. When hunting alligators became illegal, • the specie made a huge comeback.

• They showed up in swimming pools, drainage ditches and retention ponds. People were even feeding them.

• Alligators began to consume ducks, hunting dogs, pets, pigs, deer, cattle, wading birds, and people!

EPA

10.By 1977, alligators were removed from endangered status to threatened status. Hunting with a permit is now allowed.

13.On farms, reproductive rates have increased 4 fold, growth rates have doubled, and unplanned mortality reduced by 34%.

Alligator serve a vital role in the ecosystem and are tied to a healthy food web.

FWS

11.The advantage of generalist species is their wide niche and habitat choices.

12.Competition from other species is their only disadvantage.

3.2 KEYSTONE SPECIES

2. Keystone specie have a central role in the functioning of an ecosystem and the existence of other species are closely tied to them.

1. The alligator is a keystone specie in the swamps, wetlands, and river systems of southern states.

3. Alligators are the top carnivores in the food web and feed on nearly every animal in or around water.

4. Alligators are keystone because they:

• dig holes that fill with fresh water; other animals use the holes for drinking and habitat

• make nesting sites that are later used by egrets and herons

• make pathways to the water, keeping grassy areas open for drainage and use by other animals

• eat predatory fish that cause a decrease in bass and bream

5. Reptiles share these characteristics:

• 3 chambered heart (except the alligator has 4 chambers)

• cold blooded - warm habitats improve metabolism

• integument has scales and some can shed their skin

• breathe with lungs

• bony skeleton

• skutes are used for protection and thermoregulation

Order Crocodilia is composed of:

1. Crocodiles • have a pointed snout and

lay eggs in holes. • They are native to Africa,

India, Indonesia and southern Australia.

2. Alligators • have a rounded snout and

lay eggs in above ground nests.

• They are larger and are darker in color than the crocodiles.

3. Caimans • have short, up-turned

snouts and large eyes.

• They are native to Venezuela and the south Amazon basin.

4. Gharials (gavials)

• have small flat heads and a very long, thin, pointed snout.

• They are native to the larger rivers in India.

Alligator Crocodile Gharlal

5. The American Alligator is the largest specie in the Order. Females lay 20-70 leathery eggs in a mound of vegetation.

6. As the vegetation decomposes it gives off heat. The incubation temperature determines the gender of the young.

Reptiles have an amniotic egg with a membrane to prevent drying out. Eggs below 85oF hatch into females, while those above 95oF become males. After 65 days the eggs begin hatching.

7. The young signal the mother with chirping sounds. She will help them crack the shells and will eat the unfertilized eggs.

The young are transported to the water either in her mouth or riding on her back. They hide in her mouth for protection.

8. In 1967, the American Alligator was placed on the endangered species list. In less than 10 years, it was reclassified to threatened in Florida, Louisiana, and Texas where 90% of the alligators live.

By limiting hunting and farming the species for its meat and hides their populations quickly grew.

The alligators’ return is one of the most successful stories in wildlife conservation.

3.3 SPECIE INTERACTIONS

1. Indicator species serve as an early warning for environmental problems.

2. Birds are excellent indicator species.

They are found almost everywhere and respond quickly to environmental changes.

3. Historically, canaries were used to detect low oxygen levels in mine shafts. The term is now synonymous with indicator species.

4. The interaction of species gives a good picture of the stability of an ecosystem. Species interact in 4 ways:

Competition •usually leads to adaptations or new species “survival of the fittest”. It is a limiting factor.

NASA

• interference - limit another’s access to resources

ex: establishing a territory

• exploitation - one specie is better at getting resources

ex: lions are better at attacking larger prey than leopards

• exclusion - similar species can’t occupy the same niche

ex: nutria vs. muskrat’s territory

• Humans have often resorted to exclusion (using one specie to get rid of another), but the introduction of non-native species, called exotics, has usually resulted in disaster.

ex: Kutzu was used as a ground cover along highways, but it is only eaten by goats.

Avoidance - finding ways to reduce competition

• resource partitioning - limiting themselves to territories not already used

ex: birds dividing up a tree, nocturnal-diurnal patterns of reef fish or mammals.

• character displacement - species have special features that cause different feeding habitats or locations

ex: bill shape and size on birds

• Predation is harmful to the individual prey but necessary at the population level to prevent any specie from over-running the habitat and to weed out sick and injured.

Symbiosis•living in close association with others• parasitism (+ -) one benefits

by harming another

ex: lamprey on fish

NOAA

Hooks on a lamprey mouth

• mutualism (+ +) both benefitex: tickbird on rhinos; one gets a meal - the other gets ticks removed

• commensalism (+ o) one benefits, other not affected

ex: bird’s nest in a tree; tree height provides protection - no benefit nor harm to tree

3.4 BACKYARD BIRDS

Phylum: Chordata

Class: Aves

There are over 8,500 species of birds in 27 different Orders. 1. A common way to

visually group them is by:• waterfowl• aerialist

• marine birds (both long and short legged waders)

• birds of prey

• fowl-like birds

• song birds and non-singing land birds

2. Anatomical adaptations:

• Body shape is adapted for flying, hopping, running, diving, tipping, floating, wading, tearing flesh, hunting, drilling and for least resistance.

Hummingbirds and sparrows are very small3-7 inches.

Canadian geese and swans are large - over 25”.

• Wing shape is used for identification. Long wings are common on migratory ducks and heavy birds.

Short wings are found on woodland birds because they take up less room in a crowded forest and aid in lift off from the water.

• Tails may be rounded, forked or squared off.

• Waterfowl bird legs are positioned behind its center of gravity; good for swimming but makes walking slow.

• Wading bird legs are tall and thin.

• Songbirds have feet that “lock” so they don’t fall out of trees.

• Bones have hollow spaces to reduce weight in flight. The neck is flexible but the rest of skeleton is rigid so they don’t wobble in flight.

• Lungs contain extra air sacs that may collapse during a dive; oxygen is stored in the blood and muscles.

• Heart is 4 chambered, is warm blooded (around 104-107 o F), and beats 135 - 1000 times/minute depending on the species.

3. Birds must eat large quantities of food to get energy for flight and to regulate temperature.

4. Their diet may be • small animals (snails, fish, amphibians, reptiles,

rodents, mollusks, worms, insects, other birds) • plant products (nectar, sap, grass, roots, leaves,

pollen, seeds, tubers, fruit, and buds).

FWS

Digestive system is poor; materials pass through in 2 hours.

6. Migration in waterfowl and songbirds • greatly increases the ecological flexibility. They do

not have to adapt - just move. Their range is where they can be found over the course of a year.

5. Flying in a V formation reduces air resistance and conserves energy.

Some fly by rapid wing beats, gliding, soaring, or hovering.

Some need a running start to become airborne and to land, others can lift out of the water.

• Internal hormonal clocks regulate migration in response to climate, stars, photoperiod and earth’s magnetism. Unusual weather may have drastic results.

The Migratory Bird Treaty Act protects 93% of the 777 species of birds including wading birds, birds of prey, shorebirds, sea birds, and perching birds.

7. Plumage• Male birds have more colorful plumage to attract

females• Female birds are camouflaged to blend in with a

nest.8. Songs and displays are used for sex identification, to

claim territory, and to attract mates.

iii. Albumin (egg white) and color for the eggshell are produced by the oviduct wall.

9. Egg • The egg is produced in a

single ovary. • Fertilization takes place at

the junction of the oviduct and ovary.

• Eggshells i. are made of calcium and

magnesium salts andii. contain channels for the

exchange of respiratory gases and water vapor.

Some birds will lay one egg per day whether it has been fertilized or not. Other lay continuously until the clutch size is reached.

USDA

10.Nesting habits • brood parasites- lay their eggs in the nests of

other birds. Ex: Cowbird

• Altricial birds - born blind, without feathers and helpless. They hatch quickly but take more time in parental care. (Ex: song & marine birds)

• Precocial birds i. hatch more slowly but

fully mature in a few hours.

ex: waterfowl

iii. In 1973, Conrad Lorenz won a Nobel Prize for his work in animal behavior that described the window of time after hatching for effective imprinting. His work touched off the “nature vs. nurture” debate.

ii. Precocial chicks and waterfowl copy the mother’s activities in an irreversible type of learning called imprinting.

3.5 SUCCESSION

1. All ecosystems age in a (theoretically) predictable way called succession.

• resilience (ability to bounce back)

• constancy (ability to live within the resources)

• inertia (resistance to change)

Often stability is maintained by change. Older organisms die leaving younger ones to replace them.

2. Stability is based on three parameters, but scientists disagree whether stability must include all three.

However, nature is very random.

3. Rain forests • High inertia

because of high specie diversity, but low resilience.

• nutrients are stored in the vegetation rather than in the soil.

• Once the forest is cut, recovery is very slow. This is another reason why cutting rain forests for farming is a bad idea.

• The soil is very poor.

4. Grasslands• low inertia with low diversity - only grass.

• high resilience because nutrients are stored in the roots, which helps them grow back quickly.

5. The four stages of succession are:

• pioneer - begins with soil formation; small plants and species with minimal requirements

• juvenile communities - low diversity

• mature communities - high diversity

• climax communities – stability; some scientists argue that climax communities don’t exist

This is the way ponds become meadows and meadows become forests.

The animal populations also change with the environment.