UNIT 4 ANIMAL

POPULATIONS

4.1 POPULATION DYANAMICS

Population dynamics describes constant changes in:

1.Size •increased growth comes from births and immigration; •decreases come from deaths and emigration. •Carrying Capacity

It is the maximum population that a habitat can support over a given time period.

Size is limited by availability of resources and niches Population growth slows as K is reached.

•Technological, social and other cultural changes have extended human’s range - but how long will it last?

• S-Curve Growth either indicate growth

with fluctuations above and below K,

or cyclic growth where the rate changes as the population increases.

• J-Curve Growth indicate exponential

growth where populations overshoot resources and crash; also called irruptive;

has random spikes and crashes.

The problem is that early growth curves may look like S when they are actually J.

• Populations are limited in their capacity for growth in two ways:

a. R-strategists: (R=reproductive potential) • These species have high

birth rates; little parental care, reproduce quickly; and have cyclic growth rate

• ex: rodents, insects

b. K-strategists: (K= carrying capacity)• These species have low

birth rates; high parental care; mature slowly; and have stable growth rate

• ex: large mammals

2. Density

• is the number of species per habitat space.

• Dense populations tend to have lower birth rates and higher disease rates.

• However, this tends to bring high populations back down.

• There is controversy over whether predators actually control the density of the prey, or vice versa.

• Density independent factors are climate, natural disaster and growth requirements.

• Density dependent facts are competition, migration, predation and symbiosis.

3. Dispersion - uniform or random distribution, or clumping of populations due to availability of resources or niches

4. Age distribution is based on how many individuals are reproductive and how long they stay that way. Show in survivorship curves or age structure histograms.

• A survivorship curve indicates trends in populations related to the number of individuals at each agea. late loss - living long after

reproductive age. ex: humans

b. constant loss - deaths are about equal at all ages. ex: birds

c. early loss - fish have short life cycles, but are reproductive most of their life

4.2 NATURAL SELECTION

1. Populations change because of adaptations to • the environment• natural selection• Mutations.

2. Speciation is the formation of new species from an older species.

3. Speciation - extinction = biodiversity.

4. 3 kinds of Adaptations:• Morphological -

specialized structures for habitat, camouflage ex: ducks with webbed feet

• Physiological - specialized functions. ex: venom in spider

• Behavioral - migration, mimicry like these wings with “eyes”

Hardy-Weinberg Law of Population Genetics.The Law lists criteria that would have to happen for the gene pool NOT to change.

1.Mating would have to be random.

2.There could be no mutations.

3.There could be no immigration (entering) or emigration (exiting) an ecosystem so the number of genes remained constant.

4.Populations would have to be large because the Law of Probability is more accurate when the sample is large.•Since all of these criteria can never be met, change will occur.

New species arise from:1.Geographic isolation - a small group separated from the main population will rotate only a few genes. ex: a canyon separates squirrels and a new specie develops

2.Reproductive isolation - some birds show a preference for particular colors, dances or displays.

3. Adaptive radiation - species move out of home range like the finches

4. Convergence - different species in same habitat develop similar characteristics.

– ex: fish and whales

5. Co-evolution - adaptations based on dependence to another organism.

– ex. clownfish and anemone

Natural Selection Results when individuals best suited to the environment are able to survive.

3 types of natural selection:

1.Directional selection • entire population moves

toward an extreme • ex: giraffes with longer

necks survive better

2. Stabilizing selection• survival favors being average• ex: large mice may need too much food, and have

trouble hiding; tiny mice may be too weak to find food - being average-sized might be better

3. Diversifying selection –• extremes are better able to

adapt• ex: gray peppered moths did

not blend with the environment; black and white moths had an advantage during the Industrial Revolution because they matched buildings better

• Mutations are random genetic accidents; may be beneficial or harmful but they change the population’s characteristics.

4.3 AMPHIBIANS

AMPHIBIANS & THE ENVIRONMENT1.Amphibians are an indicator species who have survived for 350 million years.

2.This long history indicates their adaptability to environmental changes.

3.Their decline on every continent where they live, suggests declining environmental health.

4.Fossil records indicate 10 different Amphibian Orders, whereas today there are only 3 Orders. Frogs, toads, and salamanders compose two Orders and the third contains the worm-like caecilians.

5. The most common frog was Rana pipens, the Leopard frog.

6. Amphibian populations are declining due to:• increased UV radiation from

ozone depletion• chemical poisoning from

pesticides and fertilizers• acid rain• competition from predators and

exotics

7. Humans have altered the environment so that predators and exotics have access to new habitats and compete with frogs both as predators and for prey.

8. Class Amphibia is important to ecosystems because they are used for prey by other species and have commercial value as medicine.

9. Contrary to legends, warts are from viruses - not frogs or toads.

AMPHIBIAN LIFE CYCLE1.The word Amphibian means double life. They must spend part of their life in the water and part on land. Generally, the larvae remain in water, while adults live on land.

2.All Amphibians must return to the water for reproduction. Their egg has no shell and is part of a jelly-like mass that must be kept moist.

3. The eggs are dark on the top half and light on the bottom half. Larvae have a round, heavy-looking body with a thin tail.

4. As metamorphosis continues, the tail is reabsorbed and hind legs appear. Front appendages appear shortly before the tadpole becomes an adult.

5. Tadpoles are herbivores.

6. Adults eat insects and small lizards.

GENERAL CHARACTERISTICS OF AMPHIBIANS1.Moist skin - can exchange gases through the skin

2.Two nostrils - connect to the mouth and lead to the lungs

3.Adults use lungs for respiration, while larval stage has gills.

4.Three-chambered heart and cold blooded circulation

5.Delicate, bony skeleton

6. hibernate in burrows in cold weather; aestivate to escape summer heat or drought

7. many are nocturnal

8. life-span between 4-15 years for toads

4.4 FATAL SUBTRACTION

Hyacinth Macaw

IMPORTANCE OF WILD SPECIES1.Wild species are important for their economic, medical, scientific, ecological, aesthetic, and recreational value.

2.Wild tropical plants provided 90% of today’s food crop seeds; 80% of medicines came from plants that were wild.

3. Bioethics is the right of any species to exist. The average specie lasts about 4 million years.

4. Background (normal) extinction rate is about 3 species per year. Currently, it is 1000 times that amount.

CAUSES OF SPECIES DECLINE1.habitat loss or fragmentation (primary factor)

2.human population growth

3.pest and predator control

4.harvesting wild plants

5.hunting, fishing, poaching

6.for sale to collectors and as exotic pets

7.pollution and related diseases

8.exotics have altered habitat giving other species new advantages

3 LEVELS OF DECLINING POPULATIONS1.Local Decline - no longer found in one native area but are found elsewhere in the world.

2.Ecological Decline - specie is present but can’t play its role in the ecosystem

3. Biological Declinea. Threatened - declining in

numbers

b. Endangered• too few individuals, extinction

soon• Species need 10,000 organisms

to maintain evolutionary potential.

c. Extinct• means gone forever - when

numbers drop below 1,000 for animal species and 120 species for plants

• the species is considered extinct because of the problems finding mates.

• Populations are doomed when the death rate is greater than the birth rate.

• These organisms have fallen below their minimal viable population size.

• They will become extinct unless change occurs somewhere.

4.5 ENDANGERED SPECIES

ENDANGERED SPECIES ACT (1973)1.“Conserve and restore endangered and threatened species and the ecosystems upon which they depend.”

2.It requires protection for any endangered or threatened species take precedence over economic concerns.

3.The Department of the Interior, acting through the U.S. Fish and Wildlife Service (FWS), is responsible for protecting most threatened and endangered species.

4. The number of endangered and threatened species went from 92 to 963 between 1973 and 1995.

5. Then, from 1995 to 1996, Congress banned any more listings.

6. Only 21 species have recovered enough to be reclassified to threatened and 11 species have been recovered enough to be removed from the list.

7. However, 40% of the species are stable or improving.

8. The ESA has been unpopular with industry, developers, miners, and timber ranchers, who contributed nearly $1 million to support repealing it.

9. However, the ESA has had no negative impact on U.S. economic development.

10.Funding costs each adult about 25 cents per year.

The Number of Endangered Species by Vertebrate Class and Most Affected Specie in Each Group

OTHER TREATIES & LAWS1.Migratory Bird Treaty Act

• prevent the destruction of non-game migratory birds or eggs.

• considers some 170 species to be “game birds,” less than 60 species are typically hunted each year.

• The most common are ducks, geese, pigeons and doves.

2.In 1993, Sec. of the Interior, Bruce Babbitt launched a national biological survey of wild species.

3. The 1975 CITES Treaty, Convention on International Trade of Endangered Species, bans commercial trade of an agreed list of endangered and threatened species.

METHODS OF WILD SPECIES PROTECTION1.Ecosystem approach - protects the whole habitat

2.Species approach - captivity breeding

3.Wildlife management - may involve moving species, regulating hunting, harvesting

IMPROVING SURVIVAL ODDS1.Captive breeding programs

2.Egg pulling for relocation in a safe place

3.Regulating hunting with licenses and habitat protection

4.Exclusive economic zones for commercial fishing

5.Protection of migratory bird flyways

6.Fishing quotas

7. Zoos currently only house 27 endangered populations of more than 100 individuals, but zoos also create problems:a. They have limited space

for larger populations who need greater habitat space.

b. Individuals can’t go back home if their habitat is gone.

c. Animals in zoos can’t fulfill their roles in the ecosystem.

4.6 MANATEES

MANATEE FACTS:1.The Florida Manatee has been protected by state law since 1893 and by the Endangered Species Act of 1973 - but only about 3000 still survive.

2. Manatees are related to the elephant. There were 5 populations in the Order Sirenia.

a. West Indian Manatee - Trichechus manatus migrates from Brazil to Florida

b. West African Manatee - coastal, freshwater of Africa

c. Amazonian Manatee - freshwater in Amazon basin

d. Dugong - found in Australia and Indonesia, has a different tail

e. Stellar Sea Cow - hunted to extinction within 27 years of its discovery in 1741 in the Bering Strait

3. The average manatee is 10 feet and weighs 1000 pounds. Calves are around 4 feet and weigh 60 pounds.

FWS

FWS

4. They like warm, shallow water and need fresh water to drink. Constant eating helps clear navigational channels of water weeds.

5. In freshwater, they encounter boats where 50% of their deaths are from human-related boat accidents.

6. Many manatees are identified by their boat propeller scars.

7. Manatees are herbivores, who eat 100 pounds of sea grass a day or 10 % of their total body weight.

8. They have large lips to hold plants and replaceable molars.

9. Because they have no predators, no social structure is present - not territorial. Herds have no leader and no permanent bonds are formed for mating.

MANATEE’S MAMMALIAN CHARACTERISTICS1.Whiskers (vibrissae) on the snout are used to rake in plants

2.Mammary glands - cows nurse their young for a year

3.Live births – the gestation period is 13 months. They produce one calf every 3-5 years and don’t reach sexual maturity until 5-9 years old

4.Warm-blooded with four chambered heart

5.May live up to 60 years

6. Large brain - poor vision, hearing is primarily in a different range from humans

7. Compartmentalized, ruminating stomach

8. Breathe air - may dive for 20 minutes

9. Marine mammal tail – horizontal paddle

10.Can produce a high-pitched whistle and clicks for communication

4.7 Wildlife

Management

FWS

WILDLIFE MANAGEMENT OFFICER:1.Manage sustainable biological resources is the function of the wildlife officer.

2.These scientists manage the water, space, food and shelter to benefit wild populations and enhance human enjoyment of them.

3. The manager needs to know the habitat requirement of the managed species, which can be grouped into 4 areas:

a. Early successional animals - those who require weedy, pioneer plants in areas that have been disturbed by fire, volcanoes, or human activity.

b. Mid-successional – • Those who benefit from abandoned cropland and

open areas created by farming, logging, road-building activities that create an edge effect.

• Edges, called ecotones, provide a transitional zone for animals such as deer that feed in clearings but can escape to the forest for cover.

c. Late-successional species - prefer old growth forests and need larger spaces

d. Wilderness species - need undisturbed areas with mature vegetation

5. Managers use techniques such as planting seeds, clearing brush, building artificial nests, and improving ponds to create and restore habitats.

GAME MANAGEMENT & HUNTERS1.There is conflicting interest in the public between the advantages of diversity vs. density.

2.Bird-watchers want diversity. Hunters want density.

3.Game animals are 10% of the wild species, but 90% of the money spent on wildlife goes to this group.

FWS

4. Funds for state game management come from the sale of hunting and fishing licenses and from taxes on hunting and fishing equipment.

5. There are over 16 million sports hunters in the U.S. who contribute significant money to support research, and to buy, restore and maintain wildlife habitats.

6. Without hunting season, some wild species would exceed their carrying capacity and starve.

7. Opponents say that wildlife management creates a surplus of game animals but not predators who present a safety issue for humans and livestock as well as reducing game species.

FWS

8. Thinning populations is then required because we have altered the food chain.

9. The Migratory Bird Hunting and Conservation Stamp Act (1934) • requires duck stamps

for waterfowl hunters.• The revenues are used

to buy and manage their habitat.

GAME MANAGEMENT & FISHING1.The fishing industry also has severe management concerns.

2.Over-fishing has resulted from enforcement issues, subsidies for upgrading fishing fleet equipment, and short-term economic needs.

3.Managers have tried to reduce over-fishing by setting quotas, dividing the allowable catch by the number of commercial boats, and by regulating the type of fish methods and gear.

4. Exclusive Economic Zone (EEZ)• The area 200 nautical miles off

shore is the Exclusive Economic Zone (EEZ) of the adjacent country. Foreign fleets are allowed only by permission.

• However, beyond this legal jurisdiction, usage of the high seas is set by international laws and treaties.

• Enforcement is very difficult because if one fleet doesn’t take the maximum catch, someone else will. (Tragedy of the Commons)

5. Sport-fishing is managed with fishing licenses, seasons, quotas, and the natural migration of fish.

6. Hatcheries and stocking programs improve inland waters, but the high seas are much more difficult.

7. The International Whaling Commission is a good example of interest in managing whale populations after 8 of the 11 major species were driven to commercial extinction.

8. However, compliance is voluntary and whales are no longer available. The U.S. stopped whaling in 1970.