Contemporary Issues in Biology LAB EXAM 2

What is the most dangerous animal in the USA, based on human deaths caused by that animal?

Bees/Wasps

Why would an animal attack a human?

• We invade their territory

• Habitat loss and development

• We threaten their young

• Poaching, collecting, and accidents

• We look like food

• Wrong place, wrong time!

Are humans a typical food source of any animals?

Humans are NOT a typical food source for any animals

Describe how to identify each of the dangerous spiders from class visually

• Black Widow

  • Neurotoxin

  • Jet black, glossy body

  • Large, round, globe-shaped abdomen

  • Signature marking: bright RED HOURGLASS on the BOTTOM of the abdomen

  • Long solid-black legs, no banding

  • 8 eyes

  • Found in dark, dry spaces

• Brown Recluse

  • Hemotoxin

  • Uniform tan/brown, matte body

  • Signature marking: dark brown VIOLIN shaped on the TOP of the cephalothorax (front section)

  • Oval, flat abdomen

  • Only 6 EYES in 3 pairs (most other spiders have 8)

Copperhead - Pit Viper

• Distinctive hourglass-shaped crossbands — wide at the sides, narrowing to a point at the center of the back — in copper/brown tones on a lighter tan/pinkish background

• Copper-colored triangular head, noticeably wider than the neck

• Generally NOT aggressive; bites are rarely fatal. Will give a waning bite with little venom (“dry bite”)

• Fun fact: Southern copperhead venom contains a protein that halts cancer cell growth in mice and prevents metastasis - potential medical value!

Cottonmouth/Water Moccasin - Pit Viper

• Short, fat, and drab — dark olive, brown, or nearly black body. Pattern is wide at the base and narrows at the top

• When threatened, coils body and opens mouth wide exposing the bright white cotton interior — this is the key ID feature that gives it its name

• Has a dark “Zorro mask” stripe on the side of the face; ridge above the eye gives it a mean/heavy-browed look; slot/oval cat-eye pupil

• World’s only semi-aquatic viper. Swims on TOP of the water and NEVER submerges. Basks on land, not in trees

• Stands its ground when threatened and coils/exposes fangs — does NOT chase

Rattlesnake - Pit Viper

• Rattle on the tail — shaken as a warning when threatened. The only Texas snake with this feature

• Heavy-bodied, keeled (ridged) scales, triangular head

• Texas species from slides: Western Diamondback (large, diamond pattern down back, black-and-white banded tail), Timber Rattlesnake (large, chevron pattern, yellow/brown/black), Pygmy Rattlesnake (very small), Western Massasauga (small)

• Shakes rattle as warning; bites are rarely fatal if treated promptly; MANY different species exist

Texas Coral Snake - NOT a Pit Viper

• Bright red, yellow, and black bands circling the entire body. Red bands touch yellow bands

• “Red on yellow, kill a fellow” (coral snake - dangerous) vs. “Red on black, friendly Jack” (milk snake - harmless)

• Small, rounded, black head (NOT triangular). No loreal pit. Round pupils. No true fangs (small fixed front teeth)

• Venom → powerful NEUROTOXIN - can cause respiratory failure and cardiovascular failure — potentially fatal

• Symptoms can be DELAYED up to 12 hours after a bite, so people may feel fine and delay treatment. Antivenom is available

• Related to cobra

• Behavior: Secretive and not aggressive; rarely bites unless handled

Pit Viper Identification

Which snake bites will lead to fatality if left untreated?

• All the dangerous snakes studied (Copperhead, Cottonmouth, Rattlesnakes, and Coral Snake) can be fatal without treatment

• HOWEVER, the Coral Snake is considered especially dangerous because its venom is neurotoxic and symptoms may be delayed, causing people to underestimate the bite

• The Eastern Diamondback Rattlesnake has the most potent venom by volume

• Copperhead bites are rarely fatal with prompt treatment

What are the symptoms of black widow and brown recluse spider bites? How are the symptoms different?

• Black Widow (Neurotoxin) symptoms:

  • The venom attacks the nervous system

  • Symptoms include immediate pain at the bite site, then systemic muscle cramps and spasms (especially the abdomen), sweating, nausea, elevated blood pressure, and chest tightness

  • The bite itself looks relatively minor (two small puncture marks, mild redness/swelling)

• Brown Recluse (Hemotoxin) symptoms:

  • The venom destroys blood cells and tissue (hemotoxic)

  • Initially painless, the bite develops into a bull’s-eye lesion with necrosis (dead, rotting skin) and a deep ulcer

  • Systemic symptoms (fever, chills, rash) can occur but local tissue destruction is the hallmark

• Key Difference: Black Widow → NEUROTOXIN = systemic nervous system/muscle effects, minor local wound; Brown Recluse → HEMOTOXIN = severe local tissue/skin necrosis, minor systemic effects

How much does food production need to increase to meet estimated demands in 2050?

Food production must double to meet 2050 needs based on our current consumption efficiency

What is the expected global population in 2050?

Global population will exceed 9 billion by 2050 (current population: 8 billion)

What is carrying capacity? Are we close to the carrying capacity for humans on earth?

• Carrying capacity is the maximum population size that an environment can sustainably support given available resources (food, water, space)

• We are approaching or may have already exceeded Earth’s carrying capacity for humans in some respects, particularly regarding resource consumption and environmental degradation

What is the main reason for clear cutting in the Amazon rainforest?

• The main reason for clear-cutting in the Amazon rainforest is to create agricultural land, specifically cattle ranching and soybean farming (used largely for animal feed)

What are some positive impacts using GMOs can have on crops? What is an example of a GMO crop?

• Benefit to Humans:

  • GMO (Genetically Modified Organisms) = higher crop productivity

  • Less pesticide use (at least short term)

  • Add nutrition to foods

• Examples:

  • Golden Rice — engineered with Vitamin A

  • Bt corn — engineered with the Bacillus thuringiensis gene to produce its own insecticide

What does crop diversification and crop rotation on farms result in?

• Crop diversification and rotation result in improved soil health, reduced soil depletion, natural pest and disease control, reduced need for chemical fertilizers, and increased farm resilience to climate variability

As countries become wealthier, how do people’s diets shift?

• As countries become wealthier, people shift towards diets higher in animal products (meat, dairy)

What are the causes of food waste? How does this differ between wealthy and developing countries?

• Wealthy countries: Waste occurs mainly at homes, restaurants and supermarkets — spoilage, over-purchasing, restaurant/household over-preparation

• Developing countries: Waste occurs mainly between producer and consumer due to inadequate refrigeration, transportation, and storage infrastructure

Should unfarmed lands (tundra, desert, rainforest) be turned into croplands? Why?

• No. Converting tundra, deserts, and rainforests into croplands is generally not recommended

• These ecosystems provide critical services: carbon sequestration, biodiversity habitat, water regulation, and climate stabilization

  • Destroying them for farmland would likely worsen food insecurity long-term and accelerate climate change

• Better solutions include reducing food waste, improving crop yields on existing farmland, and shifting to more plant-based diets

True or False: Some bacteria are resistant due to random chance

TRUE; antibiotic resistance arises from random genetic mutations that occur naturally (random mutations in bacterial DNA can → antibiotic resistance)

Would using antibiotic hand soap lead to more or fewer antibiotic resistant bacteria at a global scale?

• Using antibiotic soap would lead to MORE antibiotic-resistant bacteria at a global scale

• Widespread use creates selection pressure that kills susceptible bacteria while allowing resistant strains to survive and proliferate

Can antibiotics be used to treat viruses?

NO (viruses lack cell walls, which antibiotics block cell wall formation; antibiotics only work against bacteria)

What was the first antibiotic and who discovered it? Has this antibiotic lost effectiveness over time? If yes, why?

• The first antibiotic: Penicillin

  • Produced by a mold

• Discovered by Alexander Fleming in 1928

• Yes Penicillin has lost effectiveness over time because many bacteria have evolved resistance to it

  • Methicillin-resistant Staphylococcus aureus (MRSA) is a well-known example

Why are antibiotics used in animal populations and what is a consequence of this?

• Attempt to prevent spread of disease

• Causes animals to grow bigger

• May contribute to bacterial resistance to antibiotics

If you are prescribed antibiotics should you take the full dose, why?

• Yes, you should take the full dose

• Not finishing a course of antibiotic kills weak bacteria, but allows the strong to survive

• Not only are you still sick, but you are now spreading the stronger, more antibiotic resistant bacteria!

What is the cause of TB (tuberculosis)? Has TB developed antibiotic resistance?

• TB is caused by the bacterium Mycobacterium tuberculosis

• Yes, TB has developed antibiotic resistance

  • Multi-drug resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) are serious health threats, partly due to incomplete treatment courses

How do antibiotics target bacteria?

• Block cell wall formation

• Prevent protein synthesis

• Prevent bacterial replication

Do human cells have cell walls?

Human cells do NOT have cell walls

What are the benefits of forest fires?

• Cleans forest floor and returns nutrients to soil

  • Removes underbrush and debris

  • More sunlight reaches ground

  • Returns nutrients to soil

  • Reduces competition among trees & undergrowth

  • Reduces risk of future catastrophic fires

  • Fewer & healthier trees = (pre-settlement conditions)

• Provides habitat for wildlife and encourages a new generation of seedlings to grow (secondary succession)

  • Fire clears heavy brush

  • Stimulates growth of grasses and small herbaceous plants (forbs)

  • Creates “snags” (standing dead trees) which provide nesting habitat

  • Increases water supply in streams due to additional run-off (fewer plants absorbing water)

• Kills diseases and harmful insects

  • Fire kills diseases and insects that prey on trees

  • More trees die each year due to diseases and insects than from fire

What are consequences of forest fires?

• Releases smoke that can cause respiratory problems

• Pollutants in the smoke can damage crops

• Run-off from burned areas pollutes the drinking water

• Extensive smoke impairs visibility of drivers can cause accidents on highways

• Reduction in tourism dollars

• Carbon monoxide

What is the impact of forest fires on soil erosion?

• Forest fires increase soil erosion

• Vegetation normally holds soil in place; when it burns away, exposed soil is vulnerable to erosion by rain and wind

• Burned soil also loses organic matter and becomes hydrophobic (water-repellent), causing more runoff

What is the impact of forest fires on pine trees with pinecones?

• Some forests depends on fire

• Ponderosa Pine & Lodgepole Pine

  • Serotinus Cones: Cones open when stimulated by heat

  • This releases seeds onto newly cleared, nutrient-rich soil, giving them an ideal germination environment. Fire is essential for these species’ reproduction

What is secondary succession? What are the stages of succession?

• Secondary succession: succession that begins after a disturbance event clears the community but leaves the soil intact

• Secondary succession → Pioneer species → Intermediate species → Climax community

What are examples of pioneer species?

• Predominant vegetation can tolerate high levels of sunlight

• Pioneer species are annuals, such as grasses and perennials, wildflowers

  • These help with soil stabilization and prevent erosion

• Some of these species require heat or smoke exposure to germinate

What is a climax community? Does it include young or old trees?

• An ecological community in the final stage of succession, in which the species composition remains relatively stable until a disturbance such as fire occurs

  • Some species require these types of communities to thrive

• Climax community: mature forest

Which kind of fires (ground, surface, crown) are beneficial, which are harmful? Why?

• Ground fires: Burn slowly through organic material (leaf litter, roots) in the soil. Generally beneficial — low intensity, recycle nutrients, clear debris without killing mature trees

• Surface fires: Burn along the forest floor through underbrush. Can be beneficial (controlled burns, clears competition) or harmful if intense

• Crown fires: Spread through the tops (canopy) of trees. Highly destructive — kill mature trees, destroy wildlife habitat, and are very difficult to control. Considered harmful