Foundations of Life
What is the molecule in a cell that carries the genetic code from the nucleus to the ribosome?
mRNA
What are the two reactants that enter a mitochondrion during aerobic cellular respiration?
Glucose + Oxygen
What type of cell division produces two genetically identical daughter cells and is responsible for growth and repair?
Mitosis
What term describes the maximum number of individuals of a species that an ecosystem can support?
Carrying capacity
What is the term for a heritable trait that increases an organism's ability to survive and reproduce in its environment?
Adaptation
What is the name of the process by which a living organism maintains a stable internal environment despite changes in its external surroundings?
Homeostasis
Photosynthesis is the process by which plants convert ______ energy into _______ energy stored in ________?
. . . LIGHT energy into CHEMICAL energy stored in GLUCOSE
What is the term for a specific segment of a DNA molecule on a chromosome that carries the instructions for building a particular protein?
A gene
What term describes the role or "job" that a species plays within its ecosystem, including what it eats and how it interacts with other organisms?
Niche
What are the two types of evidence (one molecular and one structural) that scientists use to support the theory of common ancestry between species?
DNA/molecular evidence and homologous structures (anatomical evidence)
What type of feedback loop is responsible for the release of oxytocin during childbirth, in which the response amplifies the original stimulus rather than reversing it?
Positive feedback loop
What happens to the carbon atoms in a glucose molecule during cellular respiration (what form are they released from the cell)?
The carbon atoms are released as carbon dioxide (CO₂) gas through the process of cellular respiration.
What process during meiosis involves the exchange of DNA segments between homologous chromosomes, creating new combinations of alleles?
Crossing over
What is the term for the gradual change in a community of organisms over time following a disturbance, such as the progression from bare ground to a climax forest?
Ecological succession
What do homologous structures (such as the forelimbs of a bat, whale, and human) reveal about the evolutionary history of those species
They reveal that those species share a common ancestor. The same underlying bone structure (humerus, radius, ulna, carpals) was inherited from that ancestor and modified over time by natural selection for different functions (flying, swimming, and grasping).
What is the correct sequence of events by which the information in a gene is used to build a protein?
(including the names of the two processes and the molecules involved)
Transcription produces mRNA from the DNA template in the nucleus; the mRNA travels to the ribosome where translation assembles amino acids into a protein based on the mRNA codon sequence.
Why does only 10% of the energy stored at one trophic level transfer to the next, and what happens to the remaining 90%?
90% is lost primarily as heat through the organism's own metabolic processes (cellular respiration, movement, maintenance). Only the energy stored in new body mass transfers upward.
If two parents are both heterozygous (Tt) for a dominant trait, what is the probability that an offspring will express the recessive phenotype, and what genotype produces that phenotype?
25% probability; the recessive phenotype is produced by the tt genotype (homozygous recessive).
How do keystone species maintain ecosystem stability, and what can happen to biodiversity when a keystone species is removed?
Keystone species exert a disproportionately large influence on ecosystem structure relative to their abundance (often through predation or habitat engineering). Their removal can cause population explosions in prey species, overgrazing, and collapse of biodiversity (trophic cascade).
How does antibiotic resistance in bacteria demonstrate the process of natural selection, and why does resistance develop faster in bacteria than in most other organisms?
Bacteria with random pre-existing resistance mutations survive antibiotic exposure and reproduce, passing resistance to offspring. Resistance evolves faster in bacteria because their generation time is extremely short (minutes to hours), meaning many generations occur rapidly.
How does a single nucleotide mutation in a gene lead to a non-functional protein, and why might two different mutations in the same gene produce proteins with very different levels of dysfunction?
A nucleotide mutation changes an mRNA codon, which may insert a different amino acid into the protein chain. This alters the protein's folding and shape, disrupting its function. Two mutations can produce different levels of dysfunction because one may affect a critical active site while the other falls in a less essential region, or one may cause misfolding while the other is silent and doesn't change the amino acid at all.
How do photosynthesis and cellular respiration together maintain the cycling of carbon between the biosphere and the atmosphere,
AND what (/how do) human activities disrupt this balance?
Photosynthesis removes CO₂ from the atmosphere and fixes it into organic molecules (glucose) in the biosphere. Cellular respiration (by all organisms, including decomposers) releases that carbon back to the atmosphere as CO₂. Human activities (burning fossil fuels and deforestation) release geologically stored carbon into the atmosphere far faster than photosynthesis can reabsorb it, increasing atmospheric CO₂ and disrupting the natural balance.
How can two cells in the same organism (with identical DNA sequences) develop into structurally and functionally different cell types, and what molecular mechanism makes this possible?
All cells contain the same DNA, but gene expression is regulated by transcription factors and other molecular signals that turn specific genes on or off in each cell type. A muscle cell activates genes for contractile proteins (actin, myosin) while a neuron activates genes for neurotransmitter production. Different proteins produced from the same DNA create cells with entirely different structures and functions (differentiation).
How can the removal of a top predator from an ecosystem trigger a trophic cascade that affects vegetation, and what does this reveal about the role of complex interactions in maintaining ecosystem stability?
When a top predator is removed, its prey population grows unchecked. The prey then overgrazes vegetation, reducing plant cover and habitat for other species. This chain reaction (called a trophic cascade) reveals that top predators indirectly regulate entire ecosystems. It demonstrates that ecosystem stability depends on a web of complex species interactions, not just resource availability, and that the loss of a single species can shift the ecosystem to a completely different stable state.
How does geographic isolation lead to speciation, and what evidence from the Galápagos finches supports the idea that one ancestral species can give rise to multiple distinct species over time?
When populations of the same species become geographically isolated, they are exposed to different environments and selection pressures. Over generations, each population accumulates different mutations and adaptations through natural selection. Eventually the populations diverge so much genetically that they can no longer interbreed, so they have become separate species (speciation).
In the Galápagos, finch populations colonizing different islands faced different food sources, which selected for different beak shapes. The 13 distinct finch species today (all descended from one ancestor) demonstrate this process of adaptive radiation.