Lecture Notes-07 Biology 1004
North Arkansas College
Topic: Human Population
- Immigration
- U. S. World population 267,000,000.
- estimated that by 2050 the population would be 307,000,000.
- 800,000 immigrants yearly in the United States
- on this basis there will be about 387 million people in the year 2050.
- Population Growth through History
- In developed countries the annual growth rate is .4%.
- In developing countries the annual growth rate is 1.8%.
- Some parts of Africa have a growth rate of 3%.
- Prior to the 1700’s the growth rate was very small and an explosion occurred beginning in the 1950’s approaching the exponential and the J curve.
- In 1804, the world population was 1billion, in the next 123 years, it doubled and in the next 48 years, it doubled again, Today the population is about 6 billion, In 2050, it is estimated to be about 8.5 to 11 billion.
- Effects of population growth
- Quality of life
- Earth’s environment
Some people today believe that the population growth is the primary factor that is responsible for problems.
Others would argue that there is an overuse of natural resources.
Both factors contribute to pollution and loss of habitat.
Communities and their Interactions
Communities is the interaction of all the populations that occupy an area.
These may interact to indicate the following:
Ecologically Dominant Species
There are a few species that are dominant in a given community usually these are small plants however, some animals can be the ecological dominant.
Keystone Species
One in whose absence would cause a major change in the community these are usually called predators.
Biodiversity
Refers basically to the complexity of species of the present 3 factors that contribute to biodiversity.
- variety of species.
- distribution of individual species.
- variety of genetic determinants.
Effects of Predator and Parasitism on Communities
- remove the least desirable species.
- enhances the species.
Evolutionary Aspects of Predator-Prey Relationships
Competition leads to evolution of new defenses by prey and the predator must also change Co-Evolution is common among predator-prey: example-spine-worm or frog fish.
Mimicry: the prey or predator changes to mimic other species for survival.
Two Types of Mimicry:
- Batesian Mimicry- prey changes to look like another species for protection example: harmless syrphid fly mimicks the bumble bee.
- Mullerian Mimicry-several species that have superior protection begin to all look alike and come to provide a learning experience to each other Commensalism: two species live together with benefits to one of them.
Mutalism: two species live together with benefits to both examples: cowbird and oxpecker.
Co-evolution: two different species evolve at the same time and provide benefits and survival example: flowering plant and it is pollinated with insects and birds
Succession in Communities
Succession is a series of replacements at the site until a final state of stability is reached.
Two Types of Succession
Primary Succession; starting stateforms are brought to naked earth rock, wind by birds.
Example: Eruption of Mt St Helens
Secondary Succession: representation of a state in which an area is cleared discarded and new species would appear.
Example: trees growing in a cleared field or pasture
Climax Succession: interdependent development of stable ecology.
Energy flow thru all living systems:
- All living organisms must have an energy source.
- This energy is in the form of a chemical bond energy released as ATP. 8,000-12,000 calories per molecule.
- There are 3 levels of Organization in energy production:
- producers are autotrophs-green plants self energy fulfilling.
- consumers are heterotrophs-species consume chemical molecules formed by producers- animals, bacteria and some fungi.
- decomposers are species that break down dead or discarded matter to release nutrients that are used to make energy.
Most of the decomposers are fungi and a few bacteria.
