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Why is estimating the total number of species on the planet hard?
Classification issues: different taxonomists may have different opinions on what constitutes a species
Lack of funding for scientific research: many of unexplored places are undiscovered and unrecorded
Limited access to remote and inaccessible habitats: some groups of organisms are more difficult to study than others
What human activities cause species’ extinction?
Habitat destruction
Introducing invasive species
Pollution
Overharvesting
Hunting
What has the loss been compounded by?
Rapid population growth
Humans can colonise many types of habitat
Humans can travel and transport species
Industrialisation has led to more rapid consumption of natural resources
Humans need food, space for infrastructure, grazing land for livestock
What are the factors leading to loss of biodiversity?
Natural hazards
Loss of habitat
Fragmentation of habitats
Pollution
Overexploitation
Introducing exotic/alien species
Spread of disease
Modern agricultural practices
Describe natural hazards as a factor leading to the loss of biodiversity
Naturally occurring events that may have a negative impact on environment
May sometimes be due to human impact when caused by climate change
E.g. hurricanes, wildfires, floods, volcanic eruptions
Describe loss of habitat as a factor leading to the loss of biodiversity
This is due to human activities like deforestation and urbanisation that leads to loss of habitat and species diversity.
This occurs when humans build or develop on a piece of land.
Describe fragmentation of habitat as a factor leading to the loss of biodiversity
This is a process wherein a large area is divided into fragments that are separated from each other by roads, towns, fields, etc.
They are isolated in a modified or degraded landscape.
There are edge effects on the fragments - there are fluctuations of light temperature and humidity at the edges as they interact with human activity as compared to the middle.
Invasion of the habitat by pests or humans increases the possibility that domestic and wild species come into contact and spread diseases.
Describe pollution as a factor leading to the loss of biodiversity
This can be in the form of:
Local pollution - spraying pesticides that drift into wild spaces, oil spills
Environmental pollution - air pollution, acid deposition, smog
Run-off from fertilisers, leading to eutrophication bio magnification of toxic chemicals in food chains
Climate change altering weather patterns
Describe overexploitation as a factor leading to the loss of biodiversity
Overexploitation due to catching, hunting and harvesting has escalated with increasing human population
If we exceed maximum sustainable yield of any species, it is unsustainable to continue exploiting it
Many species are the victims of hunting and poaching for exotic pets and products e.g. elephants
Describe introducing exotic/alien species as a factor leading to the loss of biodiversity
Humans can do this by bringing own crops or livestock to other countries
Non-native species can outcompete native ones and cause disturbances and imbalance in the ecosystem
E.g.
Rabbits in Australia were brought for game hunting but reproduces too quickly and took over the area. Viruses were introduced to kill them but did not work.
Cane toads were introduced to control pests on sugarcane but outcompeted native species
Red fox, camel, blackberry, prickly bear cactus, crown of thorns, starfish etc
Grey squirrels outcompeted red squirrels for food - transmitted disease known as squirrel pox
Describe spread of disease as a factor leading to the loss of biodiversity
Diseases of domesticated animals can spread to wild animals vice-versa
Can mutate and infect other species when they are usually only meant for one species
E.g.
Swine flu in 2010 passing from pigs to humans
Bird flu affecting both birds and humans since 2003
Foot and mouth disease affecting hooves animals spread to humans in UK 2001
Describe how modern agricultural practices is a factor leading to the loss of biodiversity
Monoculture - salinisation, loss of soil fertility
Pesticides - kill other organisms which are not pests
Herbicides - can harm the crop and may make it toxic
Genetic engineering - superweeds
Fertilisers - eutrophication
All of the above lead to pollution
What is the deforestation by humans including?
Agricutlure
Mining
Hydroelectric power
Logging
Road building and settlements
Wildfires
Coral Reef: case study
Coral reefs in Southeast Asia (Indonesia, Philippines) are highly diverse ecosystems.
Human impacts: Overfishing, pollution, climate change.
Overfishing: Depletes species, disrupts ecological balance.
Pollution: Agricultural runoff, sewage reduce water quality, stress corals.
Climate change: Causes warming, acidification, leading to coral bleaching and death.
Conflict: Balancing economic interests (tourism, fishing) with conservation efforts.
Solution: Marine Protected Areas (MPAs) can protect reefs by limiting activities and aiding recovery.
Challenge: Effective management and enforcement of MPAs are crucial for success.
Eastern Himalayas: case study example
Eastern Himalayas: Rich in unique plant and animal species found nowhere else.
- Human impacts:
Deforestation: Driven by agriculture, timber, and fuelwood; causes habitat loss and species displacement.
Poaching and hunting: Threatens endangered species like tigers, snow leopards, and rhinoceroses.
Climate change: Alters temperature and conditions, impacting adapted species’ growth and survival.
Conflict: Balancing economic development with environmental protection and conservation is complex.
Conservation efforts: Protected areas and policies aim to reduce deforestation and poaching, but face resistance from logging companies and poachers.
What are the factors that help maintain biodiversity?
Complexity of the ecosystem
Stage of succession
Limiting factors
Inertia
Describe complexity of an ecosystem
The more complex a food web is, the more resilient it is to the loss of a species or reductions in its population size
If one type of prey, predator or food source is lost, another will adapt and fill its niche
Describe stage of succession
At the colonisation stage, there are few species
Species over sixty increases until the stable climax community is reached
Species diversity increases as succession proceeds and falls slightly at the climax stage
Communities in the first few stages of succession may not be as resilient and stable as those in later stages
Describe limiting factors
If abiotic factors are in abundance, systems are likely to maintain biodiversity even if one factor reduces
If they are already in short supply, then it is more likely that species will die out if abiotic factors reduce further
Describe inertia
Inertia is the property of an ecosystem to resist change when subject to disruption
Helps determine which ecosystems will recover quickly
What are the factors making a species prone to extinction?
Narrow geographical range
Small population size or declining numbers
Few populations of the species
Large body/high trophic levels
Low reproductive potential
Seasonal migrants
Poor disperses
Specialised feeders and niche requirements
Useful to humans, living in herds
Island organisms
Describe narrow geographical range
If a species only lives in one place and that habitat gets damaged, it is easier for the species t be wiped out
Though the species can be bred in captivity, this in not a permanent solution
E.g. golden lion tamarin, lemur
Describe small population size or declining numbers (low genetic diversity)
Smaller populations have lower genetic diversity and are less resilient to change.
As numbers fall, interbreeding increases between individuals of similar genes until populations are too small or extinct.
E.g. snow leopard, tiger
Describe few populations of the species
If there are very few populations, it is easier for the species to be wiped out
E.g. lemurs
Describe large body/high trophic levels
90% of the energy transferred to trophic levels is lost as heat, leaving minute amounts for higher trophic levels.
This means that there are very few top predators (animals at the highest trophic levels) and they usually have very small populations and low population densities. This makes them vulnerable to extinction.
Describe low reproductive potential
Slow and infrequent reproduction means that the population takes time to recover from a disturbance.
E.g. blue whales, gannets, albatross
Describe seasonal migrants
Species the migrate depend solely on the habitats they migrate for an extended period of time.
If one of their habitats is wiped out, they will not have food or shelter for that period of the year, and usually have to travel far to reach their habitat. This makes them liable to extinction.
Describe poor dispersers
Species that cannot move to new habitats easily are also in trouble. For example, plants that rely only on seed dispersal and growth are vulnerable as these are both long processes and changes in biomes may occur before plants can move to a new environment.
Non-flying animals go extinct too as they may not be able to escape to other places away from introduced hunters.
Describe specialised feeders and niche requirements
Species that feed on only one type of diet can be vulnerable as they will lose their food supply completely if anything happens to the species they feed on
E.g. giant pandas only eat bamboo, koalas only eat eucalyptus leaves
Describe being useful to humans, living in herds
Species that live in large groups more liable to Overexploitation by humans as many can be exploited at once
E.g. bison
Describe island organisms
Organisms living on islands are more vulnerable as:
Populations may be small
High degree of endemic species (no other habitats)
Low genetic diversity
Vulnerable to the introduction of exotic species
What does the IUCN stand for?
International Union for the Conservation of Nature
What is the IUCN?
The global authority on the status of the natural world and the measures needed to safeguard it, assessing the conservation status of animal and plant species around the world
How does the IUCN monitor the world species?
Through the Red List of Threatened Species
What is The Red List?
A list of species under varying levels of threat to their survival - data is gathered on a global scale
What is the IUCN classification system?
Note 
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