General Biology: Characteristics of Life, Ecosystems, and Climate Change

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Characteristics of Life

Common Features of All Living Organisms

All living organisms share a set of fundamental characteristics that distinguish them from non-living matter. Understanding these features is essential for identifying life and studying biology.

Reproduction: The ability to produce new individuals, either sexually or asexually.
Growth and Development: Organisms increase in size and undergo changes throughout their life cycle.
Energy and Matter Use: All living things require energy and materials to maintain their structure and function.
Cells: The basic unit of life; all organisms are composed of one or more cells.
Order: Living things exhibit complex but ordered organization.
Response to the Environment: Organisms can sense and respond to stimuli in their environment.
Evolution: Populations of organisms change over generations through evolutionary processes.

Characteristics of Life Explained

Reproduction: Can be sexual (involving two parents) or asexual (single parent). Example: A plant started as a single cell and developed into a multicellular organism.
Energy Use: Organisms capture and convert energy to useful forms. For example, endothermic (warm-blooded) animals like reptiles do not eat as much as mammals because they lose less heat.
Cellular Organization: Some organisms are unicellular (single-celled), while others are multicellular. Example: Basal organs in Ireland represent organization.
Homeostasis: The process by which organisms maintain internal stability. Example: Elephants shiver when cold to maintain body temperature.

Response to Environment

Organisms detect and respond to changes in their environment to survive and reproduce.
Example: Evolution by natural selection allows organisms best suited to their environment to survive and reproduce.

Viruses: Are They Alive?

Viruses are not considered living because they are not cellular and cannot reproduce independently.
They rely on host cells to replicate their genetic material, similar to asexual reproduction.
Viruses evolve rapidly, as seen with COVID-19 and its variants.

Science as a Discipline

What is Science?

Science is a systematic approach to understanding the natural world through observation and experimentation.

Attributes of Science:
- Testable
- Repeatable
- Falsifiable
- Evidence-based
Scientific Method: A process involving hypothesis formation, experimentation, and theory development.
Fact: An observation repeatedly confirmed.
Theory: A well-substantiated explanation based on a large body of evidence.

Ecosystems and Ecosystem Processes

Components of Ecosystems

Ecosystems consist of all the biotic (living) and abiotic (non-living) components in a particular environment.

Energy Flow: Movement of energy through an ecosystem.
Biogeochemical Cycling: Movement of nutrients and elements through biotic and abiotic components.

Greenhouse Effect and Greenhouse Gases

Greenhouse Effect: The atmosphere traps heat, making Earth habitable.
Major Greenhouse Gases:
- Water vapor (H2O)
- CO2 (carbon dioxide)
- CH4 (methane)
- N2O (nitrous oxide)
- O3 (ozone)
- CFCs and replacements
Methane: Shorter atmospheric lifetime than CO2, but higher global warming potential. Major sources include livestock digestion.

Levels of Ecology

Hierarchy of Ecological Organization

Organism → Population → Community → Ecosystem → Biosphere
Population Ecology: Study of changes in population size, density, and growth over time.
Community Ecology: Study of interactions among populations of different species.

Population Growth Models

Exponential Growth: Rapid, unlimited growth. Number of individuals increases continuously. Represented by a J-shaped curve.
- Example: Human population growth.
- Equation:
Logistic Growth: Growth slows as resources become limited. Represented by an S-shaped curve.
- Carrying Capacity (K): Maximum population size that can be sustained.
- Equation:

Species Interactions

Competition (-, -): Both species are harmed.
Predation (+, -): One species benefits, the other is harmed.
Herbivory (+, -): Animal eats plant.
Mutualism (+, +): Both species benefit.
Parasitism/Pathogens (+, -): One benefits, one is harmed.
Commensalism (+, 0): One benefits, the other is unaffected.

Effects of Climate Change on Species Interactions

Mutualism: Example: Plant-pollinator interactions. Climate change can alter the timing of flowering and pollinator activity, disrupting mutualism.
Parasitism/Pathogens: Example: Zika virus. Climate change can expand the range of mosquito hosts.
Competition: Example: Alpine plants. Warming allows lower-elevation plants to move to higher elevations, outcompeting native alpine species.

Trophic Structure and Food Webs

Trophic Structure

Describes feeding relationships within a community.
Energy and nutrients flow through trophic levels.

Food Chain and Food Web

Food Chain: Linear sequence of energy transfer from one organism to another.
Food Web: Interconnected food chains, reflecting complexity in trophic structure.

Keystone Species

Species with a disproportionate effect on ecosystem diversity and function.
Example: African elephants maintain savanna ecosystems by removing specific trees.
Example: Sea otters in the Aleutian Islands control sea urchin populations, maintaining kelp forests.

Trophic Cascade

Occurs when changes at one trophic level affect multiple other levels.
Example: Removal of sea otters leads to increased sea urchins and decreased kelp.

Ecological Footprint and Carrying Capacity

Ecological Footprint

Amount of resources (land, water, fuel) required to sustain one person.
Expressed in hectares per person.
World average: 1.8 hectares per person.

Carrying Capacity

Maximum population size that can be supported by available resources.
Technologically advanced countries have higher ecological footprints.

Fossil Fuels and Biofuels

Fossil Fuels

Include oil, natural gas, and coal.
Formed from the remains of ancient living organisms.

Biofuels

Derived from recent living organisms (plants, algae).
1st Generation Biofuels: Produced from food crops (e.g., ethanol from corn, biodiesel from vegetable oils). May compete with food supply.
2nd Generation Biofuels: Produced from non-food biomass (e.g., wood, grasses, inedible plant parts). Require more processing.
3rd Generation Biofuels: Produced from algae and other sources that do not compete with food crops. Can be grown anywhere.

Photosynthesis and Cellular Respiration

Photosynthesis

Process by which plants, algae, and some bacteria convert light energy into chemical energy (sugars).
Occurs in chloroplasts using chlorophyll.
Overall equation:
Two main stages:
1. Light Reactions: Capture energy from sunlight, produce ATP and NADPH, release O2.
2. Calvin Cycle: Uses ATP and NADPH to synthesize sugars from CO2.

Cellular Respiration

Process by which cells break down sugars to release energy for biological processes.
Overall equation:

Photosynthesis and Respiration Quiz Example

If photosynthesis is blocked at the Calvin cycle, which molecules would not be made?
- A. Sugar
- B. O2
- C. Sugar and O2
- D. All of the above

Summary Table: Types of Biofuels

Generation	Source	Advantages	Disadvantages
1st Generation	Food crops (corn, sugar cane, vegetable oils)	Established technology	Competes with food supply, requires arable land
2nd Generation	Non-food biomass (wood, grasses, inedible plant parts)	Uses waste materials, less competition with food	Requires more processing, may need additional resources
3rd Generation	Algae, other non-food sources	Can be grown anywhere, high yield	Technology still developing

Additional info:

Some context and examples were expanded for clarity and completeness.
Equations and tables were formatted for academic study purposes.