Explaining Change

Physical Changes

changes in the state or appearance of matter that do not alter the chemical composition

Physical Changes

• Characteristics:

  • Reversible

  • No new substances formed

Melting, Freezing, Evaporation, Condensation, Sublimation

Examples of Physical Changes

Chemical Changes

changes result in the formation of new substances with different properties from the original substances.

Combustion

Burning of wood or gasoline, producing CO₂ and water.

Chemical Changes

• Characteristics:

• Usually irreversible

• Formation of new substances

• Energy changes (exothermic or endothermic reactions)

Succession

The process by which the structure of a biological community evolves over time.

Primary Succession

Occurs in lifeless areas where there is no soil (e.g., after a volcanic eruption)

Secondary Succession

Occurs in areas where a community has been disturbed but soil remains (e.g., after a forest fire).

Deforestation

Clearing of forests for agriculture or urban development.

Pollution

Release of harmful substances into the environment.

Climate Change

Long-term changes in temperature and weather patterns due to human activities such as burning fossil fuels.

Urbanization

Expansion of cities leading to habitat loss and fragmentation.

Agricultural Practices

Use of pesticides and fertilizers.

Mutations

Changes in the DNA sequence of an organism

Point Mutations

Changes in a single nucleotide (e.g., substitution, insertion, deletion).

Mutations, Genetic Variation

Genetic Changes

Chromosomal Mutations

Changes in the structure or number of chromosomes (e.g., duplications, deletions, inversions, translocations).

Genetic Variation

Differences in DNA sequences among individuals within a population.

Natural Selection

Speciation

Evolutionary Changes

Natural Selection

The process by which organisms with favorable traits are more likely to survive and reproduce, passing those traits to the next generation

Speciation

The formation of new and distinct species in the course of evolution

Allopatric Speciation, Sympatric Speciation

Speciation types

Sympatric Speciation

Occurs without geographic separation, often through genetic or behavioral differences.

• Example: Certain plants can undergo polyploidy, where the number of chromosomes doubles, leading to reproductive isolation from the parent population.

Allopatric Speciation

Occurs when populations are geographically separated.

• Geographic isolation

• Genetic drift

• Natural selection

• Mutation

• Sexual selection

Factors Influencing Speciation

Concentration, Temperature, Catalysts,

Factors Affecting Rates

Surface Area

Greater surface area increases the rate by allowing more particles to collide

Reversible Reactions and Equilibrium

Reactions that can proceed in both forward and reverse directions.

Impact of Humans on the Carbon Cycle

Combustion of Fossil Fuels

Deforestation

Agricultural Practices

Carbon Sequestration

Carbon Cycle

Movement of carbon between the atmosphere, hydrosphere, biosphere, and geosphere

Nitrogen Cycle

Movement of nitrogen between the atmosphere, soil, and living organisms

Carbon Cycle, Nitrogen Cycle, Water Cycle, Phosphorus Cycle

What are the Biogeochemical Cycles