Populations Flashcards
Limiting factors
Limit the growth of a population size
- water
- food
- space
- light
- oxygen
- predators
- disease
- competition
They prevent populations from exceeding the carrying capacity
Population growth curve
S shaped curve
- Lag phase
- Log phase / exponential phase
- Stationary phase
K strategists
- Believe population size is determined by carrying capacity
- limiting factors exert an increasingly more significant effect as carrying capacity is reached
E.g. larger animals and plants
- Low reproductive rate
- Slow development
- Late reproductive age
- Long life span
- Large body mass
R strategists
Population size increases very quickly
Carrying capacity exceeded before limiting factor have an effect
Build up of water can poison the species (boom and bust
E.g. mice, insects, spiders, weeds
- high reproductive rate
- quick development
- young reproductive age
- short life span
- small body mass
Boom and bust
Some species exceed their carrying capacity due to a rapid reproductive rate. Once they have exceeded this, there are insufficient resources to maintain the population and some will die. Death can also be caused by the build up of waste products
Predator prey relationships
- prey population increases when predator numbers are low, and low environmental resistance with few limiting factors
- more prey = more food for predators
- populations of predator increases after a lag time
- prey eaten by predators = prey numbers decrease
- less food for predators, fewer survive and predator numbers decrease
- cycle repeats
Intraspecific competition
Within the species
• as environmental pressures increase (factors become limiting) competition increases
• Those best adapted survive, reproduce and pass on their genes (others die)
• Keeps the stationary phase fairly stable
Interspecific competition
Between species
Competitive exclusion
Explains why particular species only grow in certain places
Conservation
The protection and management of ecosystems so that natural resources in them can be used without running out
Preservation
The protection of ecosystems so they’re kept exactly as they are
- nothing is removed from from a preserved ecosystem, and they’re only used for activities that don’t damage them
How does increasing human population threaten biodiversity
- over exploitation of wild populations for food
- disrupting habitats with urbanisation and pollution
- introducing non native species which competitively exclude native species
In situ
• protected areas, national parks, nature reserves
• Marine Conservation Zones
• Controlling/preventing introduction of species that threaten local biodiversity
• Protecting habitats e.g. coppicing to control water levels to conserve wetlands
• Restoring damaged areas e.g. coastlines polluted by oil
• Promoting particular species e.g. by protecting nesting sites or food sources
• Giving legal protection and endangered species
Ex situ
zoos
• Relocating organisms
• Breeding in captivity and reintroducing to the wild
• Botanical gardens- controlled environments
• Seed banks
What are SSSI’s
Sites of special scientific interest
4 reasons for conservation
- social
- economic
- ethical
- ecological
Economic reasons for conservation
Ecosystems provide lots of resources that humans need e.g. rainforests -species providing resources such as drugs, clothes and food.
These are traded at a local and global scale. If not conserved, resources could be lost and there would be less trade in the future
Some species have indirect value e.g. pollinators
Social reasons
Recreation and ecotourism give high social and economic value from the aesthetic side of ecosystems e.g. birdwatching and walking
Habitats may be lost if not conserved, so future generations won’t be able to enjoy them
Ethical reasons
Some people believe all species have a right to exist and we are obliged to conserve environments
Often ethical arguments are ignored in favour of economic arguments governments - conservation is often driven by economics
Ecological reasons
Helps to prevent climate change e.g. when trees are burnt, CO2 is released which contributes to global warming. Conservation of trees slows this
Disrupting food chains also has a knock on effect on other organisms
Large scale timber production
• clear felling is completely cutting down all of the trees in an area. It is for large scale timber production
• Trees take up water from the soil which stops the soil being washed away (soil erosion) and polluting rivers. Keep nutrient levels in balance in the carbon and nitrogen cycle. Clear felling leads to the opposite
• If trees are felled on a rotation of 50-100 years then biodiversity can be increased but this isn’t cost effective
Sustainable production
Harvesting in amounts which leaves sufficient organisms to grow and replenish what has been harvested
- it can be carried on indefinitely via replanting, coppicing…
Sustainable forestry- large timbers
- replant a tree for each one harvested
- whole woodland must maintain its ecological function of biodiversity, climate, mineral and water cycles
- local people should benefit from the forest
Balance needed between making money and maintaining biodiversity
How to ensure max. yield
- control pests and pathogens
- only plant tree species that will grow well in the area
- plant trees optimal distances apart to prevent too much competition for light, water, minerals
Coppicing- smaller timber
Cutting a tree trunk close to the ground to encourage several new, thinner stems to grow
- once they have grown, the new stems will be cut
- all this thin wood can be used for furniture, firewood… but the trees don’t die and so no replanting is needed
Rotational coppicing - smaller timber
Woodlands are divided up and different sections are coppiced on different years.
• This means each section is at a different stage and coppicing can be done to provide a continuous supply of wood each year.
• By the time they are ready to coppice the first section again, the shoots should have regrown and be ready to be re‐cut.
‘Standards’ are trees left uncoppiced and cut to produce larger timber for planks etc. ‐ these have more value
2 methods of managing fish stocks
- Fisheries
- Aquaculture
Aquaculture
Breeding, rearing and harvesting of plants and animals in all types of water environments including ponds, rivers, lakes and ocean
- restricts impact on oceanic fish stocks
- expected to feed more people than traditional fishing in future
Fisheries
- high economic value (sales and jobs)
Marine Stewardship Council has 3 main principles for sustainable management:
1. Over fishing must be avoided to stop extinction of species
2. No permanent damage to local habitats
3. Always comply with local, national and global regulations
What are the advantages and disadvantages of aquaculture, rather than ‘capture fisheries’?
Advantages
- restricts the impact of fishing on oceanic fish stocks
- is a cheap and plentiful protein source for an increasing human population
Disadvantages
- populations susceptible to pests and pathogens
- possible cause of pollution.
State 2 reasons the forests in the Terai region has been under pressure
- Expansion of agriculture into forested areas, grazing from farm animals, over exploitation of forest resources
- replacement of traditional agricultural crop varieties with modern ones
State 1 reason the forests in the Terai region are important to local communities
The forests provide people with a sustainable source of fuel, animal feed, food building materials, agricultural and household tools and medicines
State 2 of the community forestry initiatives introduced by the WWF and Nepalese gov.
- Conservation of the forest landscape. To ensure conservation with development, they introduced community forestry initiatives in which local people had rights to exploit the forest as well as responsibility to look after it.
- Scheme also introduced biogas plants and wood efficient sticks to reduce demand for firewood
1 advantage of a partnership between conservancies and tourism in the Maasai Mara
Use money from tourism for conservation
1 disadvantage of a partnership between conservancies and tourism in the Maasai Mara
Tourism may destroy the land
