Biology of food

Explain how evolution by natural selection can result in the amazing biodiversity on the planet

Natural selection acts on natural variations present within populations. When environmental conditions favor certain advantageous traits, individuals carrying those traits survive and reproduce at higher rates. Over generations, these heritable traits accumulate, driving evolutionary divergence and resulting in the immense biodiversity seen on Earth

Animals

Humans primarily consume herbivorous or omnivorous animals (e.g., cows, pigs, chickens) rather than apex carnivores because significant energy is lost at higher trophic levels. Dietary choices are also influenced by cultural perception and social stereotype models (e.g., lower warmth/competence perceptions)

Plants

Humans eat cultivated crops (e.g., tomatoes Solanum lycopersicum) while avoiding toxic wild relatives (e.g., nightshade Atropa belladonna)

Fungi

Edible forms (e.g., chanterelles, honey mushrooms, yeast) are consumed, whereas poisonous lookalikes (e.g., Jack o'lanterns, Galerina) contain toxic compounds produced to ward off pests

Lactifluus & lactobacilus - fungi lactates milk

• Micellular form-yeast

Bacteria

Beneficial bacteria like Lactobacillus are used in fermented foods, while pathogenic strains like certain E. coli are avoided

• Microbes no nucleus

Protists

• Microbes w nucleus

Algae such as Spirulina, Chlorella, and red algae (Irish moss for carrageenan) are harvested directly for consumption or used as food additives

What is Biodiversity?

Biodiversity refers to the variety of life on Earth at all levels, from genes to ecosystems, encompassing evolutionary, ecological, and cultural processes that sustain life

Three Levels of Biodiversity

Genetics, Species, Ecosystem

Genetic Diversity

Variety of genes/alleles within a population or species. Importance: Protects populations from disease outbreaks and environmental shifts

Species Diversity

Number of different species in a habitat. Importance: Decreases pest damage, improves soil health, increases crop yields, and offers better nutrition

Ecosystem Diversity

Variety of habitats and ecosystems in a given area. Importance: Provides essential ecosystem services like water purification, soil fertility, and nutrient cycling

The connection between biodiversity and agriculture

Biodiversity is the foundation of agriculture. However, modern industrial agriculture relies on monocultures. Out of 390,000 plant species, only 12 crops and 5 animal species provide 75% of human food today, with rice, maize, and wheat providing >50% of plant calories. Monocultures prioritize high yield and consistency but severely reduce genetic diversity, making crops vulnerable to total devastation by diseases (e.g., Irish potato blight, Cavendish banana Fusarium wilt). Agrobiodiversity goals focus on diversifying consumer diets, supporting resilient production systems, and expanding conservation

What is a phylogeny

A phylogeny (or phylogenetic tree) is a visual diagram showing evolutionary relationships and shared ancestral lineages among biological entities (species, individuals, or genes)

3 Domains

Bacteria, Archaea, and Eukarya

4 Eukaryotic Kingdoms

Plants, Animals, Fungi, and Protists

Reading, Interpreting, and Building a Phylogeny:

• Root: The oldest common ancestor of all taxa on the tree,.

• Node: Point where a lineage splits, representing a common ancestor,.

• Taxon (Taxa): The tips of the branches representing compared organisms/genes,.

• Branch: Lines connecting nodes and tips,.

• Clade: A group containing an ancestor and all of its descendants,.

• Greatest Common Ancestor: Represented by the shared node deepest in the lineage uniting the groups in question,. Evolutionary closeness is determined by how recently species shared a node, not by their arrangement on the tips.

• Clues to Build Trees: Morphological/physical traits (bones, limbs), exact genetic/DNA sequences, and fossil record timelines

History of Apple Domestication & Spread

Apples originated in Central Asia (Kazakhstan) and spread globally. John Chapman ("Johnny Appleseed") planted seedling orchards across North America; over time, both Chapman and the apple were "sweetened beyond recognition" in folklore, mirroring how humans selectively bred tart wild apples into sweet commercial fruit.

Human-Apple Relationship & Coevolution

Coevolution occurs when species mutually drive each other’s evolution. Sweetness evolved in fruits as an evolutionary signal that the fruit is non-toxic and rich in energy. Animals (bears, humans) eat sweet apples and spread their seeds, increasing the reproduction of sweeter apple trees

Cultivation & Grafting:

Apples do not "come true" from seed because they are obligate outcrossers (require cross-pollinated genetic material) and highly heterozygous; planting a seed yields an unpredictable tree,. To maintain specific commercial varieties (e.g., Honeycrisp, Gala), growers use grafting—attaching a branch of a desired fruiting tree onto rootstock

Importance of Genetic Diversity in Apples

Grafting creates clones and stops natural evolutionary adaptation–. Relying on a handful of cloned varieties in massive monoculture orchards leaves apple trees highly vulnerable to evolving pests and pathogens, forcing growers to rely heavily on chemical pesticides or genetic modification

What is a Trophic Cascade

An ecological chain reaction where changes at top feeding levels trigger effects that ripple down through lower trophic levels, altering the entire ecosystem,. It often depends on a keystone species—one with a disproportionately large impact on its ecosystem relative to its abundance

Direct vs. Indirect Effects & Diagram Notation

• Solid Line ($\longrightarrow$): Direct interaction (e.g., predator eating prey)20,23.

• Dashed Line ($--\rightarrow$): Indirect interaction (e.g., predator indirectly helping plants by limiting grazers)20,23.

• Plus (+): Positive effect on population growth or survival20,23.

• Minus (-): Negative effect on population growth or survival (e.g., consumption or competition)20

Reading and Interpreting Cascade Example

• Yellowstone Wolves: Extermination of wolves (-) in the 1920s allowed elk populations to explode (+), causing severe overgrazing of riverbank willows and aspens (-)–. This drove out beavers (-) and led to riverbank erosion. Reintroducing wolves in 1995 preyed on elk (-), which indirectly allowed willow/aspen recovery (+), restoring beavers (+), songbirds, and river stability–,.

• Sea Otters: Otters eat sea urchins (-), indirectly protecting kelp forests (+) from overgrazing,.

• Salt Marshes: Crabs eat snails (-), indirectly preventing snails from destroying marsh grass (+)

What is Domestication?

The process of adapting wild plants and animals for human use

History & Purpose of Domestication

Domestication began ~12,000 years ago (~10,000 BC),. It allowed humans to gain control over food production, create a dependable food supply, and transition from nomadic lifestyles to permanent settlements. Dogs were the first domesticated animal (~20,000 BC). Livestock (sheep, goats, pigs, cows) were domesticated ~10,300–7000 BC in the Fertile Crescent/Middle East

How Artificial Selection Works

1. Heritable variation exists in wild populations,.

2. Humans choose individuals with preferred traits as breeding parents,.

3. Over generations, the desirable traits become predominant in the population

Testing for Heritable Variation

• Reciprocal Transplant Experiment: Growing two variants in both warm and cold environments,. If trait differences persist regardless of the environment, they are due to genetics (heritable adaptation); if traits change based on the environment, it is due to phenotypic plasticity–.

• Parent-Offspring Comparison: Comparing mid-parent trait averages to offspring averages. A strong positive correlation (slope near 1) confirms high genetic heritability

Darwin & Domestication

Charles Darwin used artificial selection in domestic breeding as a direct model to explain how natural selection works in nature over long timeframe

Corn Domestication (Popped Secret):

Genetic and archaeological evidence demonstrates modern corn (Zea mays) was domesticated in Mesoamerica from a wild ancestor grass called teosinte, which had small, encased kernels

What is Lactase Persistence?

Lactose is the sugar found in milk; lactase is the enzyme that breaks it down into glucose and galactose. While all human infants produce lactase, most humans lose this ability after weaning–. Lactase persistence is the genetic trait that keeps the lactase gene active into adulthood

Genetic & Evolutionary Causes

It is caused by mutations in regulatory regions controlling lactase gene expression–. In pastoralist communities that domesticated cattle, milk provided a critical food and fluid source during famines. Adults with lactase persistence survived at higher rates and passed on the gene, driving strong positive selection

Relationship between lactase persistence and cow domestication

Lactase persistence coevolved directly with cattle farming and dairying culture in European and African pastoral populations

Transmission vs. Molecular Genetics:

• Transmission Genetics: How traits and genes are passed down across generations (Mendelian inheritance)32.

• Molecular Genetics: How information in DNA is expressed into functional molecules (DNA → mRNA → protein

Mendel’s Laws

1. Dominance: Heterozygotes express only the dominant allele phenotype.

2. Segregation: Alleles for a gene segregate during meiosis so gametes carry only one allele.

3. Independent Assortment: Alleles of different genes assort independently during gamete formation

DNA Replication and Gene Expression

• Replication: Copying DNA every time a cell divides (mitosis/meiosis) so traits can be inherited.

• Transcription: Converting DNA sequences into messenger RNA (mRNA) in the nucleus.

• Translation: Reading mRNA at the ribosome to build protein chains

History of GMOs

Modern agriculture began ~10,000 years ago → Mendel’s laws in 1866 → Radiation/chemical mutation breeding in 1920s–1940s → First recombinant DNA in 1973 → First GMO consumer drug (human insulin) in 1982 → First commercial GE crop (Flavr Savr tomato) in 1994 → AquAdvantage salmon in 201535–36. USDA bioengineered foods include corn, soybean, canola, cotton, ringspot-resistant papaya, non-browning Arctic apples, and Bt eggplant

How Genetic Engineering (GE) is Done

1. Identify gene for a desired trait.

2. Insert gene into a vector (e.g., plasmid).

3. Transfer vector into target organism’s genome.

4. Grow organism to verify expression.

5. Transgenesis vs. Cisgenesis: Transgenesis introduces genes from an unrelated species; cisgenesis uses genes from a wild relative.

6. CRISPR-Cas9: Uses guide RNA and Cas9 enzyme to precisely cut target DNA and introduce customized edits without leaving foreign vector DNA.

7. GE vs. Selective Breeding: GE is much faster and precise because it inserts only the gene of interest without dragging along thousands of unwanted background genes,.

Why did Bill Nye change his mind about GMOs?

• (Note: The specific details of why Bill Nye changed his mind are not included in your provided slide sources; externally, he changed his mind after reviewing lab safety data and scientific consensus on GE safety.)

Steps in the Scientific Method

Make an Observation → 2. Ask a Question → 3. Create a Hypothesis → 4. Conduct an Experiment → 5. Analyze results→ 6. Form a Conclusion

Correlation vs. Causation

• Correlation: Two factors occur or change together (e.g., cat web searches vs. Amazon shipping costs).

• Causation: One factor directly produces the outcome in another. Causation can only be proven through controlled experiments that isolate variables

Confirmation bias

(Note: While mentioned on your topic list, confirmation bias is not explicitly defined in the slide text; it refers to the human tendency to search for or interpret data in a way that confirms prior beliefs, which rigorous scientific methods aim to prevent.)

Allele

Different versions of the same gene

Animal (word def)

Multicellular eukaryotic heterotrophs in Kingdom Animalia

Archaea

Single-celled prokaryotic microorganisms in Domain Archaea

Bacteria

Single-celled prokaryotic microorganisms lacking a nucleus in Domain Bacteria

Biodiversity

Variety of life on Earth across genetic, species, and ecosystem levels

DNA

Molecule storing encoded genetic instruction

Dominant

An allele that masks a recessive allele in a heterozygote

Eukarya

Domain of organisms whose cells contain membrane-bound nuclei

Fungi

Spore-producing eukaryotic organisms (mushrooms, yeasts, molds)

Gene

Segment of DNA containing instructions for a functional product

GMO

Organism modified genetics-wise; informally refers to genetic engineering

Graft

Attaching a branch from a parent plant to rootstock to clone a variety

Heterozygous

Carrying two different alleles for a specific gene. refers to having two different alleles for a specific gene, one inherited from each parent

Homozygous

Carrying two identical alleles for a specific gene.to having two identical alleles for a specific gene, one inherited from each parent.

mRNA

Messenger RNA molecule transcribed from DNA to guide protein synthesis

Phenotype

The physical expression of a trait or gene

Plant

Photosynthetic multicellular eukaryotes in Kingdom Plantae

Protein

Functional amino acid chain produced via translation of mRNA

Replication

The cell process of copying DNA prior to cell division

Teosinte

The wild ancestor grass of modern domesticated corn

Transcription

the process in which a cell copies a gene’s DNA sequence into RNA using the enzyme RNA polymerase, forming an RNA molecule such as mRNA that later guides protein synthesis

Translation

nucleotide sequence of mRNA is decoded to build a chain of amino acids. This chain later folds into a functional protein. Translating mRNA into a protein at the ribosome