Honors Biology Midterm Study Guide – Semester 2

Comprehensive vocabulary flashcards based on the Honors Biology Midterm Study Guide covering ecology, DNA replication, protein synthesis, and Mendelian genetics.

Ecosystem

The level of organization that includes all living and nonliving things in a specific area.

Producers

Organisms that make their own food; they form the base of most food webs.

Sunlight

The ultimate source of energy for most ecosystems.

Population

A group of individuals of the same species living in the same area.

Biotic factor

Any living component of an ecosystem.

Predation

An ecological relationship where one organism, like a hawk, eats another, like a mouse.

Transpiration

The process by which plants release water vapor into the atmosphere.

Nitrogen fixation

The process that converts nitrogen gas into forms usable by living organisms.

Trophic level energy density

The principle that energy decreases at each level, with the greatest amount of available energy at the producer level.

Niche

An organism’s specific role or job within an ecosystem.

Primary succession

Ecological succession that begins in an area where no soil exists.

Mutualism

A symbiotic relationship in which both participating organisms benefit.

Desert

A biome characterized by low rainfall and sparse vegetation.

Carrying capacity

The maximum number of individuals of a species that an environment can support.

Limiting factor

A factor that controls the size or growth of a population.

Decomposer

An organism that breaks down dead organic matter and returns nutrients to the ecosystem.

Secondary succession

Succession that occurs in an area where soil already exists, often following a disturbance.

DNA

Stands for Deoxyribonucleic acid; the hereditary material of most organisms.

Double helix

The twisted-ladder shape of the DNA molecule.

Adenine and Thymine

Nitrogen base pairs that always bond together in DNA.

Semi-conservative replication

The process of DNA replication that produces two identical molecules, each with one original and one new strand.

Enzymes

Specific proteins, such as those that unzip DNA, required for replication.

RNA

A nucleic acid that contains the sugar ribose and the base uracil instead of thymine.

mRNA

Messenger RNA; carries instructions from the DNA in the nucleus to the ribosome.

Transcription

The process where a sequence of DNA is copied into mRNA; it occurs in the nucleus.

Translation

The process where mRNA is decoded at the ribosome to build a chain of amino acids.

Codon

A sequence of three nucleotides on mRNA that codes for a specific amino acid.

tRNA

Transfer RNA; the type of RNA that brings amino acids to the ribosome during translation.

Point mutation

A mutation that changes a single nucleotide in the DNA sequence.

AUG

The start codon that signals the beginning of protein synthesis.

Amino acids

The individual building blocks that make up proteins.

Gene

A specific sequence of DNA that codes for a protein.

Stop codons

Nucleotide triplets that signal the end of translation.

Gregor Mendel

The father of genetics who used pea plants to study heredity.

Alleles

Different forms or versions of a gene.

Homozygous

An organism that has two identical alleles for a specific trait.

Heterozygous

An organism that has two different alleles for a trait (e.g., Tt).

Phenotype

The physical appearance or observable characteristic of a trait.

Genotype

The genetic makeup of an organism, represented by pairs of alleles.

Punnett square

A diagram used to predict the possible genotypes and phenotypes of offspring from a cross.

Gametes

Haploid sex cells produced through the process of meiosis.

Crossing over

Process in meiosis where homologous chromosomes exchange segments, increasing genetic variation.

Principle of segregation

The principle stating that alleles separate from one another during the formation of gametes.

Incomplete dominance

A genetic scenario where the heterozygous phenotype is a blend between the two homozygous phenotypes.

Codominance

A genetic scenario where both alleles are equal and expressed together, such as in AB blood type.

Sex-linked traits

Traits controlled by genes located on the sex chromosomes (X or Y).

Diploid number

The normal human chromosome count in somatic cells, which is $46$.

Haploid number

The number of chromosomes found in a human gamete, which is $23$.

Karyotype

A visual display showing the complete set of an individual's chromosomes.

Independent assortment

The law stating that genes for different traits can segregate independently during the formation of gametes.