5 Biodiversity: Genes, Diversity, Threats, and Conservation
Genetic diversity and the gene pool
Humans have two copies of each gene (one from each parent) => two alleles per gene; the collection of all alleles in a population or species is the gene pool.
If genetic diversity declines, the gene pool shrinks, increasing extinction risk and reducing adaptive potential.
Founder effect: small founder populations can reduce genetic variation; example discussed: the Amish, traced to a single family.
Discussion point: in the event of catastrophic disturbances (e.g., a fire) that leave only a tiny fraction of individuals, the gene pool can drop dramatically, reducing evolutionary options for the population.
The role of males and females in diversity and reproduction:
Males contribute genetic variation to a population via sperm; genetic diversity is partly signal of the mating pool.
Females contribute the eventual offspring outcome (the next generation).
The biologic function is to produce the next generation; the Creative emphasis on male genetic variation is the source of diversity, while female investment shapes offspring production.
Theoretical maximum number of offspring for a female: about across a lifetime (starting around age and ending around ; assuming monthly ovulation, one egg per cycle). This illustrates space–population limitations on reproductive output.
Levels of biodiversity
Biodiversity is commonly described in three hierarchical levels:
Genetic diversity: variation within populations and species (alleles, genotypes).
Species diversity: variety of species present in an area; includes concepts of interbreeding and reproductive isolation.
Species are defined by reproductive isolation; to be the same species, organisms must typically produce fertile offspring with each other.
Ecosystem diversity: variety of habitats and the complex interactions among organisms and their abiotic environment (energy flow, nutrient cycling, etc.).
Important idea: diversity must be understood at multiple levels because loss at one level can cascade to others.
Species diversity and mechanisms of isolation
Species diversity depends on the ability of populations to interbreed and produce fertile offspring; many barriers reduce interbreeding (hybrid infertility, mating barriers, etc.).
Species concept emphasizes that offspring must be able to reproduce and sustain the next generation.
Ecological and evolutionary mechanisms create and maintain species diversity: mating isolation, ecological niches, and differential adaptation.
Ecological and spatial diversity concepts
Ecological diversity emphasizes the variety of organisms in a community and their interactions with abiotic factors (resources, carbon, nitrogen, oxygen, etc.).
Biodiversity is linked to the number and variety of habitats (ecosystems) and how energy and resources flow through them.
Diversity is influenced by energy availability and the number of producers in an area; energy is needed for biomass production, which in turn supports diverse life.
Time and evolutionary history matter: different regions have different taxonomic histories and rates of diversification.
Factors shaping biodiversity and distribution
Energy and primary production:
Biomass production is higher where energy input and primary producers are abundant (highest near the equator).
Energy availability and the diversity of producers influence overall biodiversity.
Evolutionary history and biogeography:
Islands show rapid speciation due to available niches and reduced competition; endemic radiations are common in island systems (e.g., Darwin’s finches in the Galápagos).
Ecological niches and speciation:
Niche differentiation (e.g., birds exploiting different seed sizes or insect types) fosters coexistence and diversification.
Disturbance regimes:
Disturbance frequency (e.g., fires) reshuffles genetic and species diversity; some disturbances can reduce diversity, while others can create opportunities for new species.
Hotspots:
Biodiversity hotspots are areas with high species diversity and many endemics, often with unique ecological and evolutionary features.
Hotspots are typically found near the equator; notable examples include tropical regions and some marine/ coastal zones.
Biodiversity hotspots and regional examples
Equatorial regions show the highest energy input, biomass production, and biodiversity (marine and terrestrial).
Costa Rica and other parts of Central America are cited as biodiversity hotspots with strong academic interest and conservation activity.
Caribbean Islands historically noted for coral reefs, though many reefs have degraded due to acidification and pollution.
Mediterranean, Brazil, Far East, and equatorial zones host notable hotspots (marine and/or terrestrial).
Inventory, estimates, and knowledge gaps
Current cataloging and sequencing efforts focus on plants, animals, and microorganisms (fungi are included but historically underrepresented).
Described species: about (1.8 million) are described or cataloged.
Estimates of total species in existence vary widely:
Approximately described species; potentially up to (10 million) total species, with substantial uncertainty.
The inventory problem is critical: without knowing total species and distributions, it is hard to quantify rates of loss or identify priority conservation actions.
Infectious agents that specifically infect humans are a small subset of overall biodiversity; the majority of biodiversity remains poorly described at the genome level.
A key takeaway: there may be a large hidden diversity of bacteria, worms, fungi, and other microorganisms that are not fully documented or understood.
Major threats to biodiversity
The overarching threat is human population expansion and associated land use, biomass occupation, and resource consumption; approximately 70% of land area and biomass is occupied by humans in many regions.
Extinction and habitat loss:
Habitat loss is a direct driver of extinction; as land is converted for human use, species lose their homes and resources.
Invasive or exotic species:
Global trade and transport introduce non-native species (e.g., poison ivy issues; insects from other countries; box shipments carrying pests like spiders, etc.).
Invasive species can outcompete native species and disrupt ecosystems.
Pollution:
Pollution harms ecosystems; historical soil pH changes (e.g., acid rain) reduced productivity and altered communities.
In some areas, dust and pollutants contribute to degraded habitats and reduced biodiversity.
Overexploitation:
Overharvesting of marine and terrestrial species reduces populations and can drive species toward extinction.
Climate change:
Global warming and associated climate shifts alter distributions, disease dynamics, and the viability of ecosystems (e.g., coral bleaching with pH and temperature changes).
Climate change can enable infectious diseases to spread to new areas (e.g., malaria re-emergence, Lyme disease expansion).
Dams and barriers:
Dams impede migratory species (e.g., salmon) from accessing spawning grounds, reducing reproductive success and genetic diversity.
Pathogens and disease spread:
Habitat loss can influence disease dynamics and facilitate cross-species transmission (e.g., influenza, coronaviruses).
The lecture emphasizes that many threats interact and compound one another, making conservation complex.
Emerging disease dynamics and habitat loss interactions
Bird flu (avian influenza) can move from birds to pigs to humans; pandemics can arise when viruses jump hosts and adapt to new reservoirs.
HIV presents a case study of high mutation rate, hindering vaccine development; adaptive pathogens pose ongoing challenges for public health and biodiversity indirectly through human behavior and ecosystem changes.
Lyme disease dynamics are shifting geographically (e.g., expansion into Canada) as winters warm and ticks survive in new regions.
The Neanderthal genome context and ancient disease resistance are mentioned as historical references for human–pathogen interactions.
Habitat disruption and loss can also influence the spread and persistence of pathogens in wildlife, with implications for humans.
Extinction concepts: mass vs background
Mass extinction: rapid, large-scale loss of many species due to a major disturbance (e.g., meteorite impact about that caused widespread dinosaur extinction within roughly hours of impact-related events).
Background extinction: gradual, ongoing loss of species at relatively low rates between mass extinction events.
Current biodiversity crisis is framed as an anthropogenic (human-caused) background extinction with potential for accelerated loss due to rapid habitat destruction, climate change, and other human pressures.
The talk emphasizes that past mass extinctions often occurred in localized regions; current changes are global and driven by human activities.
Factors that influence the risk of background extinction
Islands:
Islands often have limited ranges for species; extinction risk is higher when a species is confined to a small area.
Population size:
Small populations are more vulnerable to stochastic events, genetic drift, and inbreeding depression.
Habitat tolerance:
Generalists tolerate a wider range of conditions and disturbances; specialists with narrow niches are more vulnerable if their niche disappears.
Disturbance regimes:
Recurrent disturbances (fire, human activity) can reshape communities and alter extinction risk.
Overall, these factors help determine whether a species experiences background extinction or is pushed toward locally or globally extinct forms.
Invasive species and notable case examples
Poison ivy: a familiar invasive problem in some areas with high coumarin production causing skin allergies.
Exotic species in Florida and Pennsylvania (snakes, mice, mosquitoes, etc.); specific examples include the Asian tiger mosquito and other introduced pests.
Aquatic and terrestrial examples include introductions of grass carp, long-horned beetles, and Canada thistle; these invasives alter habitats and outcompete natives.
Australia example: intentional introduction of rabbits led to subsequent ecological problems; later controls included introducing predators (rats, cats) and, eventually, diseases to reduce populations—illustrating historical strategies can create new problems.
Pollution and biomagnification
Pesticides and ecological toxins can accumulate up the food chain through bioaccumulation and biomagnification, ultimately affecting top predators (e.g., bald eagle decline in parts of the US due to DDT and related compounds).
Hormonal disruption and calcium homeostasis symptoms in birds led to brittle eggs and reduced hatch success, explaining declines in predator populations dependent on these prey species.
Acid rain and sulfur compounds contribute to soil and water acidification, altering ecosystems and biodiversity.
Climate change and biodiversity resilience
Climate change alters energy balance and atmospheric chemistry, leading to shifts in species distributions and ecosystem function.
The lecture notes that while some greenhouse effect is natural and essential for maintaining habitable temperatures, rapid anthropogenic changes are stressing ecosystems and increasing extinction risk.
The pace of temperature change and the associated ecological rearrangements challenge species’ ability to adapt quickly enough, increasing vulnerability for specialized taxa.
Conservation strategies and policy
Endangered Species Act (ESA) of 1973 (United States): a framework of laws and regulations to protect threatened and endangered species, establish recovery plans, and regulate land use and enforcement.
Recovery programs and landowner incentives: conservation often involves compensation or assistance to landowners to mitigate conflicts between human activity (e.g., agriculture, livestock) and wildlife protection (e.g., predator reintroduction, wolf management).
Enforcement and regulatory provisions play key roles in implementing conservation actions.
Ex-situ conservation and seed banking:
Seed banks preserve crop and native plant seeds as a genetic reservoir for future restoration and food security.
The noted seed storage facility is described as being in the northern part of Sweden (used to store seeds as a safeguard against catastrophic events). The concept is to maintain a living seed library to safeguard crop diversity (past and future).
Zoos and captive breeding:
Zoos and captive breeding programs can serve as a last-resort habitat for critically endangered species, though there are criticisms: limited genetic diversity, problems with reintroduction, and potential loss of natural behaviors.
Example concerns discussed include inbreeding (e.g., white tigers) and the risk that captive populations may not be well adapted to release into the wild.
In-situ vs ex-situ considerations:
Practical notes emphasize careful evaluation of whether ex-situ approaches genuinely conserve biodiversity or merely delay extinction.
Ecosystem services: value of biodiversity to humans
Four conventional categories of ecosystem services (provisioning, supporting, regulating, cultural):
Provisioning: tangible goods like food, timber, water, and medicines.
Supporting: ecological processes that enable ecosystems to function (e.g., nutrient cycling, soil formation, primary production) and water purification.
Regulating: climate regulation (carbon sequestration, temperature moderation), erosion control, and stabilization of gases (e.g., CO₂, O₂) in the atmosphere.
Cultural: recreational, aesthetic, and educational values that people derive from ecosystems.
The lecture presents ecosystem services as a framework to justify conserving biodiversity by highlighting the natural capital that ecosystems provide to people.
A common exam question arises: which term is not a general category of ecosystem services?
Correct answer (as given in the lecture): Reflecting (not a standard category; the four are provisioning, supporting, regulating, and cultural).
Bioprospecting and natural product discovery
Bioprospecting: searching for new organisms that produce useful secondary metabolites for medicines, agriculture, or industry.
Examples touched on in the talk:
Frogs: amphibian peptides with antimicrobial properties; amphibians have produced antimicrobial peptides with potential therapeutic value; ongoing exploration includes isolating and synthesizing these compounds.
Reproductive tract peptides: certain female reproductive system peptides demonstrate antibacterial activity (illustrative of host defense peptides).
Horseshoe crab blood: cobalt-based (blue) blood used in tests to detect bacterial endotoxins (the lysate test); historically linked to medical advances for ensuring sterility; mentioned as contributing to medical science and potential disease treatments.
Bioprospecting also emphasizes the broader idea that biodiversity is a reservoir for potential therapeutics, industrial products, and agricultural innovations.
It is also noted that some organisms (e.g., certain frogs) have yielded peptides with antibiotic properties, illustrating why protecting biodiversity can have direct practical benefits.
Species richness, community structure, and biodiversity metrics
Species richness in a community refers to the number of different species present and their relative abundances.
Example framework: compare three communities (A, B, C) with different species distributions to illustrate richness and evenness:
Community A: several species with varying abundances (dominance by one species).
Community B: more equal representation across species (evenness higher).
Community C: low richness (fewer species) but possibly even distribution.
Biodiversity contributes to community resilience: higher species richness and functional redundancy can enhance resistance and resilience to disturbances.
Conservation status classifications and data interpretation
The international community uses formal classification systems to assess extinction risk; the lecture references the International Union for Conservation of Nature (IUCN) system as a framework for evaluating species status.
Threatened categories discussed include: Vulnerable, Endangered, and Critically Endangered; and broader categories describe levels of concern.
Practical data point: current inventories suggest about described species; around (roughly ) are considered threatened within a subset of assessed species.
The Red List and related inventories provide critical information for prioritizing conservation actions and identifying gaps in knowledge.
Summary and practical takeaways
Biodiversity operates on multiple levels (genetic, species, ecosystem) with energy availability, evolutionary history, and niche specialization driving patterns of diversity.
Human activities—habitat loss, invasive species, pollution, overexploitation, and climate change—are the dominant drivers of current biodiversity loss, with the potential for cascading ecological and health effects.
Conservation strategies range from policy (Endangered Species Act), to ex-situ safeguards (seed banks and zoos), to in-situ habitat protection, and to incentive-based approaches for landowners.
Ecosystem services provide a concrete rationale for conservation by highlighting benefits like provisioning resources, regulating climate and water, maintaining ecosystem health, and supporting culture and recreation.
The ongoing challenge is improving inventory accuracy, understanding regional variation, and implementing integrated conservation actions that address multiple threats simultaneously.
Quick quiz reference
Which of the following is not a general category of ecosystem services? Answer: Reflecting (categories are provisioning, supporting, regulating, and cultural).
Key numerical references (for quick review)
Alleles per gene: copies per gene (one from each parent).
Maximum theoretical number of eggs for a human female: across a lifetime, starting around age and ending around .
Described species: about .
Estimated total species: range from to potentially , with substantial uncertainty.
Biodiversity hot spots: highest near the equator; examples include Central America (Costa Rica), Caribbean islands, the Mediterranean, Brazil, and the Far East.
Last mass extinction event: years ago due to meteorite impact in the Gulf of Mexico; disruption occurred within roughly hours.
Population land use: humans occupy about of land and biomass in many regions.
pH examples related to pollution: historical soil pH declines from around to about (and coral reef pH decreases from toward in some discussions).
Seed banks and ex-situ storage concept: northern Sweden (seed collection site referenced in lecture).
Endangered status notes: roughly threatened species within the evaluated subset (~ assessed).
References and terms to remember
Gene pool, alleles, founder effect, bottlenecks
Levels: genetic diversity, species diversity, ecosystem diversity
Ecological niches, island biogeography, speciation dynamics
Species richness and evenness concepts
Mass vs background extinction; anthropogenic drivers
Invasive species and biosecurity issues
Pollution effects: bioaccumulation and biomagnification; DDT and bald eagle example
Climate change impacts on disease spread and ecosystem stability
Conservation policy: Endangered Species Act (1973); ex-situ seed banks; zoos as conservation tools
Bioprospecting and antifungal/antimicrobial peptides; amphibian peptides
Ecosystem services categories: provisioning, supporting, regulating, cultural (not reflecting)