BIOL116 Lecture #21 (11/24/25) (11/26/25)

What formula captures the impact (I) of a human population on the environment ?

The formula is I = P A T, where:

• P is the number of people

• A is average income

• T is level of technology

What is the first anthropogenic stressor?

Habitat destruction, fragmentation, modification, degradation

What is the second anthropogenic stressor?

Change in nutrients and resource availability

What is the third anthropogenic stressor?

Chemicals (pollution)

What is the fourth anthropogenic stressor?

Eutrophication

What is the fifth anthropogenic stressor?

• Pathogens

What is the sixth anthropogenic stressor?

Overexploitation

What is the seventh anthropogenic stressor?

Invasive species

What is the eighth anthropogenic stressor?

• Climate change

Ranking of ecological footprint by country

1. China

2. USA

3. India

4. Russia

5. Japan

What does the ‘Human ecological footprint’ measure?

It measures the amount of land area (global hectares) and energy needed to support an average citizen of a nation

According to the provided material, what is the greatest threat to the world’s species?

Habitat destruction is the greatest threat, followed by overexploitation

What term describes the process where a large continuous habitat is reduced in area and divided into two or more fragments?

habitat fragmentation

In habitat fragmentation, the area of different vegetation or land use introduced between fragments is known as the ___

matrix

What is ‘effective population size’ (N_e)

It is the size of the population estimated by the number of its breeding individuals, which is usually lower than the total population size (N)

What is the term for the process where toxic chemicals in water become successively more concentrated at higher trophic levels?

Biomagnification

The accumulation of a substance, such as a toxic chemical, in various tissues of a living organism is known as ___

bioaccumulation

What does this image show?

An example of bioaccumulation

What is eutrophication?

It is the increase in nutrient levels in a water body, which has sifniciatn effects on aquatic communities, often leading to algal blooms

During eutrophication, wat is the direct consequence of the massive increase in phytoplankton like cyanobacteria and algae?

They cover the upper sunlit layer of the water, which can block light to organisms below.

What environmental problem is produced when industries release large quantities of nitrogen and sulfur oxides that combine with atmospheric moisture?

Acid rain, which is a combination of nitric and sulfuric acids

ON the pH scale, a substance with a pH less than 7 is considered ___, while a substance with a pH greater than 7 is considered _

acidic; alkaline

What is definition of overexploitation or overharvesting?

It is a harvest that exceeds the productive capacity of a species, causing its population to decline over time

What Latin American tree species, also known as caoba, is mentioned as being overexploited for its wood?

Broad leaf mahogany (Siwetenia macrophylla)

Why was the American bison (Bison bison) hunted almost to extinction by European colonizers and who

native Americans

What is the ‘Tens Rule’ regarding invasive species?

Roughly 10% of imported species escape, 10% of those establish populations, and 10% of established species become problematic.

What are the five defining characteristics of an invasive species listed in the material?

• not native

• established

• abundant

• spreading

• has negative effects on local species or ecosystems

A disease-producing pathogen that moves from an animal species to humans is known as a __

zoonosis

According to the source, what percentage of emerging pathogens are zoonotic

75%

The HIV virus, which causes AIDs, is an example of a zoonosis that jumped to humans from what type of animal?

Nonhuman primates, such as chimpanzees.

What term is used to describe the human introduction of pathogens or hosts into new areas?

Pathogen pollution

Why did vulture populations (Gyps spp.) decline in India, Pakistan, and Nepal?

They were consuming cattle carcasses containing the anti-inflammatory drug diclofenac, which is a toxin to them and caused kidney failure.

What is the purpose of inserting a gene from the bacterium Bacillus thuringiensis (Bt) into corn?

The gene produces proteins that are toxic to certain insects, making the corn resistant to pests.

For what purpose were cane toads (Rhinella marina) organically produced to Australia?

They were introduced as a form of biological control to combat beetles that were damaging sugar cane crops.

How do activities like deforestation and mining create environments suitable for disease-transmitting mosquitoes?

These activities create more spots that collect rainwater, providing ideal breeding grounds for mosquito larvae.

The Black Death, which killed over a third of Europe’s population in the 14th century, was caused by what bacterium?

The bacterium Yersinia pests

What environmental impact related to plastic waste was a consequence of the COVID-19 pandemic?

The widespread use of masks, gloves, and other single-use medical supplies led to a significant increase in plastic pollution

How can air pollutants form industrial processes cause water bodies to become more acidic?

Pollutants like nitrogen and sulfur oxides combine with moisture in the atmosphere to form nitric and sulfuric acids, which then fall as acid rain.

As acidity in water bodies increases, there are __ effects on fish, tadpoles, etc.

lethal

What should I takeaway from this graph about pH in aquatic environments?

• Most aquatic life thrives in pH from 6.5 - 9; survival drops outside of range

• Acid rain lowers pH, which prevent fish from spawning or fish death

• Human activities and pollution an shift pH, affecting lake productivity and ecosystem health

What should I takeaway from this slide about habitat fragmentation?

• Habitat fragments act like islands - small size and greater isolation reduce species colonization

• Closer and larger fragments = more biodiversity (easier for species to move and survive)

What is the first thing that habitat fragmentation depends on?

Number of isolated patches

What is the second thing that habitat fragmentation depends on?

size of patches

What is the third thing that habitat fragmentation depends on?

• connectivity of patches

What is the fourth thing that habitat fragmentation depends on?

• nature of matrix between patches

What is the fifth thing that habitat fragmentation depends on?

ecology of individual species

What happens when birds, marine mammals, and many other ocean animals when they are covered by crude oil following spills?

They sicken and die.

More reproductive individuals of a species are better for __

conservation

Why is the effective population size N_e lower than the total population size (N):

• inability to find a mate

• being too old or too young

• poor health

• sterility

• malnutrition

• mating system: polygyny, polyandry, etc.

What should I takeaway from this slide about marine environments facing multiple threats?

• Pollution: sewage, chemicals, and excess nutrients cause eutrophication and degrade water quality.

• Fishing impacts: trawling damages seafloor habitats; bycatch harm non-target species.

• Shipping: ballast water introduces invasive species oil spills pollute marine environments

• Coastal development: alters shorelines and disrupts natural habitats

• Sediment resuspension: reduces light penetration and affects aquatic life

• Climate change: warms oceans and increases acidification, stressing marine ecosystems

Eutrophication (Oligotrophic)

• clear water

• low productivity

• very miserable fishery at large game fish

Eutrophication (mesotrophic)

• increase produciton

• accumulated organic matter

• occasional algal bloom

• good fishery

Eutrophication (eutrophic)

• very productive

• more experience oxygen depletion

• rough fish common

High reproductive rate + ___ rate = successful invasive species

high dispersal

Generalist diet + ___ and pathogens = successful invasive species

lack of predators

Tolerates disturbance and human presence and __ plastic = successful invasive species

phenotypically

Tolerance for wide range of conditions + ___ diet = successful invasive species

broad

Good competitors + __ or fast life cycle = successful invasive species

asexual

What parasitic flea, discussed in the lecture, can penetrate he skin of pigs and humans, often under the nails?

tunga penetrans

What do we have to know about tuna penetrates (flea) (extra)

• there are males and females

• this is a parasitic-like interaction

What phenomenon does this image show?

The tens rule

What should I takeaway from this side about species introduction and invasion?

• Invasive species go through stages: introduction → establishment → spread → impact

• Biotic resistance from native species can either block invasions or limit their growth after arrival