5. Ecology, conservation and climate change

What are populations?

• One species in one location at one time

• Are capable of interbreeding to produce viable offspring

• Different groups of same species must be reproductively isolated

What is reproductive isolation?

When there is a geographical barrier which prevents individuals from reproducing

What are sampling techniques used for?

Estimating population size

What are the reasons for sampling rather than counting all individuals?

• Time

• Destructive sampling

• Feasibility of counting

Why is it important that sampling is random?

• Representation

• Removal of biases

• Generalisation

What is quadrat sampling used for?

To estimate population sizes of plants and sessile animals

What are sessile animals?

Remain in one place e.g. corals, sea anemones

What is standard deviation

Measure of how spread out data is from the mean

How is the Lincoln Index calculated?

Population size = M x (N/R)

What is the protocol for capture-mark-release-recapture?

1. Random sample of population is captured and counted (M)

2. Captured individuals are marked and released

3. Second random sample of population is captured and counted (N) and number of recaptured marked individuals is counted (R)

4. Population is estimated using the Lincoln Index

What is carrying capacity?

Maximum population size of a species that can be supported long term in an environment

What factors can affect a species’ carrying capacity?

• Availability of food and water

• Space

• Shelter

• Disease

• Predators

• Climate

How can population size be limited?

• Density dependent factors

• Density independent factors

What are density independent factors?

• Do not depend on population density

• Usually abiotic

• Climate events and natural disasters

• Habitat destruction

• Seasonal changes

What are density dependent factors?

• Dependent on population density

• Usually biotic

• Competition for resources

• Risk of predation

• Disease

As population increases, density dependent factors decrease populations back to carrying capacity - negative feedback

What are the 4 factors that affect the size of a population?

• Natality (birth)

• Mortality (death)

• Immigration (entering)

• Emigration (leaving)

What are the phases of a sigmoid population growth curve?

• Exponential phase: N+I > M+E

• Transitional phase: limiting factors start affecting population growth N>M

• Plateau phase: carrying capacity is reached, N=M

What organisms can be used to investigate population growth in the laboratory under controlled conditions?

• Duckweed

• Yeast

How can duckweed be used to model population grwoth?

• Add 3 plants to a cup/beaker/container of water

• Count number of leaves every 3 days

• Plot number of leaves on a graph

How can yeast be used to model population growth?

• Add small sample of yeast to weak sugar solution

• Direct counting of yeast cells/turbidity of yeast suspension using a colorimeter

What is intraspecific competition?

• Competition for resources between members of the same species

• Increases due to density dependent factors

• Territory for feeding and reproducing

• Mates for reproducing

• Social dominance in social species

What is intraspecific cooperation?

• Benefits all members of a population

• Increases population’s access to resources and protection from predators

• Group hunting

• Group foraging

• Defence against predators

• Parenting

What is a community?

Populations of different species living and interacting with each other in an ecosystem

What are interspecific interactions?

• Herbivory

• Predation

• Interspecific competition

• Mutualism

• Parasitism

• Pathogenicity

What is interspecific competition?

• When individuals from different species compete for the same resources

• Leads to competitive exclusion

• E.g. grey squirrels and red squirrels

What is mutualism?

Close relationship between 2 organisms of different species - both individuals benefit from the activity of the other

What is symbiosis?

Close interaction between 2 different species

What is parasitism?

Form of symbiosis where one species benefits but the other is harmed

What is pathogenicity?

When an organism infects another species, causing a disease

How are root nodules in the legume family an example of mutualism?

Legume family:

• Nodules containing nitrogen-fixing bacteria

• Require nitrogen compounds

Nitrogen-fixing bacteria:

• Provides supply of nitrogen compounds

• Bacteria receives carbohydrates and other organic compounds from plant via photosynthesis

How are mycorrhizae in the orchid family an example of mutualism?

Mycorrhizae:

• Formed by symbiotic relationship between plant roots and fungus

• Enhances orchids’ ability to acquire nutrients

• Receives carbohydrates and protection from plant

Orchids:

• Grow in mineral-poor soil

• Benefit by increasing surface area for absorption of water and minerals

How are zooxanthellae in hard corals an example of mutualism?

Photosynthetic zooxanthellae algae:

• Produce nutrients e.g. glucose used by corals

• Remove waste and produce oxygen

Coral polyps:

• Provide protection

• Provide carbon dioxide for photosynthesis

What are alien species?

Organisms that have been introduced to an ecosystem and do not occur there naturally

What are invasive species?

Alien species that cause harm to the natural ecosystem

How do alien species become invasive species?

If they have a better chance of survival than the native species due to:

• Absence of predators

• Absence of diseases

• Faster rate of reproduction

• Large size/more aggressive

• Outcompeting for food/other resources

What are endemic species?

Native species

What is competitive exclusion?

No two species can occupy the same niche

What approaches can determine if competition is the reason for changes in population?

• Lab experiments

• Field studies where one species is removed

• Field observations using tests of association between two species

How do scientists test interspecific competition?

• Quadrat sampling records presence/absence of species

• Data compared using statistical tests for association

What are the hypotheses required for a chi-squared test?

• Null hypothesis: species are independent - Accept if P > 5%

• Alternative hypothesis: species are associated - Accept if P < 5%

How are chi-squared tests of association completed?

• Table of observed frequencies for 2 species using data collected with quadrats

• Identify two possible hypotheses

• Construct table of expected values

• Calculate chi-squared using observed and expected values

• Determine degree of freedom for chi-squared test

• Use chi-squared value to determine if P > 0.05 or P < 0.05

• Determine if there is an association between the two organisms

What is the chi-squared formula?

Expected Value = (Row total x Column total)/Grand total

What is the formula for degrees of freedom?

(number of rows - 1)(number of columns - 1)

How are predator-prey relationships a negative feedback cycle?

Cyclical oscillations (boom-bust cycles):

• Predator kills and eats prey → prey population decreases

• Lower prey number → predator numbers fall

• Prey recovers → predator population increases again

What are top-down controls?

• Pressures applied at higher trophic levels to control dynamics in an ecosystem

• Top predator prevents overpopulation of prey

• E.g. Wolves of Yellowstone National Park

What are bottom-up controls?

• Resources such as nutrients available to producers, affecting growth of producers

• Population growth at higher trophic levels is impacted by availability of producers

• E.g. Algal blooms

What is allelopathy?

• Release of chemicals as secondary metabolites or toxins by plants

• Given off into soil to prevent nearby competitive plants growing in same area

What are the two main components to ecosystem stability?

• Resistance - withstand change

• Resilience - recovery after disturbance

What are the requirements for stable ecosystems?

• Steady supply of energy (usually sunlight)

• Absence of disruptions interfering with sustainability

• Climatic variables within tolerance limits (temp/rain)

• Nutrient cycling without leakages

• High genetic diversity for adaptive capacity

How is the Amaoon rainforest carbon sinks?

• Generate atmospheric water vapour by transpiration

• Cools atmosphere

• Modifies air flow and wind patterns

• Impacts rainfall

• Removes carbon dioxide from atmosphere

What is the formula for percentage change?

Final - Initial / Initial x 100

What is a mesocosm?

Indoor experimental system that examines the natural environment under controlled conditions

What can mesocosms be used for?

• Study the factors that maintain stability in ecosystems

• How altering biotic or abiotic factors can lead to change

What are the advantages of investigating ecosystem stability with a natural ecosystem?

Realistic - actual environmental conditions are experienced

What are the disadvantages of investigating ecosystem stability with a natural ecosystem?

Variable conditions - minimum or nonexistent control over ‘controlled variables’

What are the advantages of investigating ecosystem stability with a mesocosm?

Able to control variables - opportunity to measure the degree of stability/extent of change in a community, investigate precise impact of a disturbing factor

What are the disadvantages of investigating ecosystem stability with a mesocosm?

Unrealistic - possibly of disputed relevance and applicability to natural ecosystems

What is included in a mesocosm?

• Autotrophs

• Consumers

• Decomposers

• Balanced photosynthesis vs respiration

What is a keystone species?

A species which has a disproportionately large effect on community structure relative to its abundance

Why are wolves a keystone species?

• Disproportionate effect on many species within the Yellowstone ecosystem

• Presence increases biodiversity of Yellowstone ecosystem

What is sustainability?

The responsible maintenance of ecological systems - no reduction of conditions for future generations, ensure long-term viability of a system

How can harvesting plants and fish from natural ecosystems be sustainable?

• Rate of harvesting < rate of replacement

• Monitor population size, age of plants/fish

• Sufficient adults to ensure enough offspring produced

• Plants - remove parts without damaging health

What is maximum sustainable yield?

Maximum average catch that a stock can sustain over a long period of time

How can scientists assess the population of fish stocks?

• Capture mark release recapture

• Echo sounders

• Analysis of fish catch

What is sustainable farming?

Methods of agricultural production that meet current needs of food production while preserving natural environment and farmland for future generations

What factors affect the sustainability of agriculture?

• Soil erosion

• Leaching of nutrients

• Supply of fertilisers and other inputs

• Pollution due to agrochemicals e.g. fertilisers

• Carbon footprint

What is eutrophication?

Natural/artificial enrichment of a body of water with nitrates and phosphates

What is the process of eutrophication?

• Excess nutrients e.g. nitrates and phosphates enter an aquatic system

• Natural runoff from soil, soil erosion, weathering of rocks

• Runoff of fertilisers

• Partially treated sewage/animal waste into waterways

• Algal bloom - blocks light for photosynthetic organisms

• Dead organisms sink to bottom of water and decompose

• Aerobic bacteria and decomposers increase BOD

• Oxygen availability for other organisms decrease, aquatic ecosystem becomes anoxic

• Decrease in biodiversity

• Algae release toxins → water not fit for drinking by humans

What are pesticides?

Chemicals used to control organisms that are a danger to crops

What is bioaccumulation?

Build up of non-biodegradable chemicals in the body

What is biomagnification?

Process by which chemical substances become concentrated in the tissues of organisms at higher trophic levels

What is DDT?

Pesticide used to kill pests

How is DDT biomagnified?

• DDT stored in fat tissue, does not readily break down

• Zooplankton eaten by fish, eaten by ospreys

• DDT accumulates in tissues of ospreys

• Causes osprey eggs to be thin

• Shells break during incubation → death of offspring

• Osprey population decreases

What is Minamata disease?

Neurological disease caused by biomagnification of methylmercury in an ecosystem

How is mercury biomagnified?

• Large fish contain higher concentrations of mercury

• Mercury converted by bacteria to methylmercury

• Methylmercury = persistent toxin, does not break down

• Absorbed by plankton, eaten by fish

What are plastics?

Range of organic synthetic materials that persist in environment because they do not biodegrade

What are the two main groups of plastics?

• Macroplastics: large, visible, more than 5mm in size e.g. bottles, bags

• Microplastics: extremely small, less than 5mm

What is the risk of plastic pollution for marine animals?

• Mistake debris for food

• Damage stomach/become lodged in oesophagus

• Cause animals to stop feeding by taking up space in digestive tract

• Can bioaccumulate in food chains

What is rewilding?

• Aims to restore degraded ecosystems back to their natural state

• Management of ecosystems to reduce human impact

• Reintroduction of apex predators and other keystone species

• Re-establishing connectivity of habitats over large areas through wildlife corridors

• Distributing seeds of plants

What are wildlife corridors?

Areas of habitat which connect wildlife populations separated by human activities or structures

How do wildlife corridors support rewilding?

• Migration

• Expanding habitat range

• Increasing biodiversity

• Greater genetic variety

What is an example of a managed natural ecosystem?

Hinewai Reserve in NZ, set up in 1987 on farmland

What is biodiversity?

Variety of life in all of its forms

What are the 3 strands of biodiversity?

• Ecosystem

• Species

• Genetic

What is ecosystem diversity?

Range of different habitats/number of ecological niches per unit area in ecosystem

What is species diversity?

Variety of species per unit area - number of species present and relative abundance

What is genetic diversity?

Variety of genes and alleles present in species - range of genetic material present in gene pool/population of species

What are the components of species diversity?

Richness - number of species in an area

Evenness - relative abundance of each species

How can fossils be used as evidence of biodiversity?

• They can be dated to give clues about the community of organisms living at a particular time in the past

• Evidence suggests that there are currently more species alive on Earth today than at any time in the past

How many mass extinction events have there been on Earth?

At least 5

What is anthropogenic species extinction?

Loss of species due to human activities

What are the anthropogenic causes of species extinction?

• Habitat destruction

• Climate change

• Pollution

• Overexploitation

• Invasive species

• Disease

What are characteristics of the giant moa?

• Lived on North Island of NZ until 500 years ago

• Large flightless birds

• Over 3m tall, over 250kg

How did the giant moa become extinct?

Overexploited - Maori people hunted for food, clothing, jewellery

What are characteristics of Caribbean monk seals?

• Distributed throughout Caribbean sea, gulf of Mexico, western Atlantic

• Declared extinct in 2008

How did Caribbean monk seals become extinct?

• Widely hunted for meat, blubber for oil, displayed in museums and zoos

• Overfishing reduced prey

• Non agressive, easy to kill

What other species are extinct because of human activities?

• Baiji

• Bramble cay melomys

• Splendid poison frog

• Pinta giant tortoise

What human activities are the cause of loss of mixed dipterocarp forests in Southeast Asia?

• Deforestation for wood

• Agriculture - palm oil plantations

• Mining of coal, metals, diamonds

• Climate change - change in rainfall patterns

• Hunting of animals for meat, skin/fur, trophies

What human activities are the cause of loss of mangroves in Florida?

• Coastal infrastructure and tourism

• Agriculture - farmers upstream releasee fertiliser, pesticides, animal waste

• Overfishing and aquaculture

• Climate change

What is the evidence for the biodiversity crisis?

• Extinction rate measured by population size, range, diversity indices

• Data via citizen science, surveys (need to be repeated)