Biology Fundamentals: Ecosystems, Energy, and Genetics

Key Ecological Definitions

• Ecosystem: A network of connected living and non-living factors.
• Population: Organisms of a specific species living together in a group or location.
• Carrying Capacity: The average number of organisms in a population that can survive in a natural environment.
• Logistic Growth: When population growth decreases as the population reaches its carrying capacity.
• Exponential Growth: Unrestricted growth of a population, usually due to unlimited access to resources.
• Keystone Species: An organism that helps define an entire ecosystem, impacting factors well beyond the standard predator/prey dynamic.
• Abiotic Factors: Non-living things in an environment (e.g., water, fire, rocks).
• Biotic Factors: Living things in an environment (e.g., predators, prey, plants).

Energy Flow and Trophic Levels

Common food chains within the ecosystem:

• Plants → Rabbits → Wolf
• Plants → Rabbits → Snake → Hawk
• Plants → Mouse → Snake

• Plants → Deer → Wolf
• Plants → Hawk → Wolf

Trophic Level Classification

Energy Transfer Efficiency

How much energy moves up each trophic level? 10%

Describe three ways organisms use obtained energy:

• Cellular respiration (released as heat)
• Releasing waste
• Increasing biomass (growth)
• Reproduction and repairing damage

Population Distribution in Food Webs

Which population is relatively small? Tertiary consumers (like the hawk) have a relatively small population because they must consume an extremely large amount of lower-level consumers and producers to obtain the energy necessary for survival. Consequently, the ecosystem cannot support a large number of organisms at this level.

Population Growth and Carrying Capacity

a. What type of growth is exhibited by this population? Logistic growth.

b. What is the carrying capacity? 7,500 (with proper reasoning).

c. Exponential growth phase: This occurs where the graph rises sharply, typically between 3,500 and 5,500.

d. Limiting factors for the seal population:

1. Increased population causes a decrease in resource availability.
2. An increase in predators or hunters decreases population size.
3. A decrease in the mating or birth rate of the young.

Biogeochemical Cycles and Climate Change

Key processes in the matter cycle:

1. Combustion
2. Respiration
3. Photosynthesis
4. Evaporation
5. Ingestion/Consumption
6. Excretion
7. Decomposition
8. Pressurization

Climate Change Links

Which processes are linked to climate change? Pressurization and Combustion. Pressurization does not occur fast enough to offset the rate at which humans are combusting fossil fuels. This causes an increase in atmospheric CO₂, which is linked to climate change.

Energy vs. Matter Movement

"Energy movement is a one-way street while matter is a two-way highway."

Matter can be recycled in an ecosystem through the Carbon, Water, and Nitrogen cycles. Atoms are used, changed, and transformed based on their position in the cycle. Energy, however, cannot be reused.

Primary sources (Autotrophs) transform radiant energy into chemical potential energy stored in glucose. Only 10% of this energy is passed to the next levels (Heterotrophs), including primary, secondary, and tertiary consumers.

Biological Levels of Hierarchy

Ranked from smallest to largest:

1. Macromolecule (Lipids, Proteins, Carbs, Nucleic Acids)
2. Organelle (Mitochondria, Chloroplast, Nucleus)
3. Organ (Stomach, Intestines, Heart)
4. Organ System (Cardiovascular System, Digestive System)
5. Organism

Genetics and Cellular Processes

• Gene: A segment of DNA that codes for a specific trait or protein.
• Chromosome: A strand of DNA coiled into an 'X' shape within the nucleus.
• Cell Cycle: The series of events (G1, S, G2, M) as a cell grows and divides.
• Codon: A three-letter sequence of nucleotides determining amino acids.
• Tumor: An abnormal mass of tissue from excessive cell growth.
• Benign: A tumor that does not spread or invade other tissues.
• Malignant: A tumor that invades tissues and spreads via the bloodstream.
• Transcription: Making an RNA copy of DNA (mRNA) to leave the nucleus.
• Translation: Bonding amino acids to make a protein using mRNA instructions.

Essential Cell Organelles

DNA Replication and Protein Synthesis

a. Complementary DNA strand:
Original: TAC GCC TTG
Complementary: ATG CGG AAC

b. mRNA Transcription: UAC/GCC/UUG

c. tRNA Translation: AUG/CGG/AAC

d. Protein Chain: Met - Arg - Asn

e. Mutation Effect: If the first 'T' in the original DNA mutated to a 'C', the tRNA would become GUG/CGG/AAC and the first amino acid would change to Valine (Val - Arg - Asn).

The Cell Cycle and Cancer Biology

Cells gather nutrients and organelles during the G1 and G2 phases. During the S phase, DNA is replicated. At the end of G1, S/G2, and M phases, the protein p53 checks the cell to ensure it has everything it needs.

If p53 is mutated, its shape changes, rendering it unable to read the DNA strand or correct incorrect base pairs. Traditionally, p53 has a butterfly shape that allows it to travel along DNA to check for errors during the S-phase.

When p53 fails, cells divide without appropriate materials or DNA checks, leading to tumor formation. Malignant tumors invade healthy tissue, hindering organ function. For example, lung tumors make it difficult to exchange oxygen and CO₂, causing fatigue.

The more cell cycles completed, the higher the chance of mutation. Because older individuals have undergone more cell cycles, they face a higher risk of cancer.