Ecology

complete

Ecology hierarchy (top to bottom)

1. ecosystem ecology (Community of organisms in an area and the physical factors with which they interact, emphasises energy flow and chemical cycling between organisms and the environment)

2. community ecology (Group of populations of different species in an area, examines the effect of interspecific interactions on community structure and organization)

3. population ecology (Group of organisms of the same species living in the same area, capable of interbreeding and sharing a gene pool, focuses on factors effecting population size over time)

4. organismal ecology (individuals)

What causes climate patterns?

latitudinal variation in sunlight intensity (sun overhead at equator, low angle at 90 degrees north and south, tropic of cancer=23.5 degrees north, tropic of capricorn=23.5 degrees south)

sunlight intensity creates global air circulation and precipitation patterns (cycle of descending dry air absorbs moisture, ascending moist air releases moisture)

Thermohaline circulation

driven by differences between water density caused by salinity and temp (cold, salty water sinks, warm, less salty water rises). thermohaline circulation causes ocean currents

Regional affects

ocean currents and mountains cause regional effects

mountain ranges

create rain shadows on leeward side of mountain (warm, moist air flows in from sea, rising air cools and releases precipitation, dry air flows inland).

Biomes

a large distinct community of flora, fauna, and abiotic factors that span multiple ecosystem. characterised by climate and subsequent vegetation in terrestrial biomes and physical environment in marine biomes.

Terrestrial biomes

climate influences plant distribution (therefore can predict climate type)

disturbance (storms, fire, human activity) influence type of biome that forms

global terrestrial biomes includes tropical forest, savanna, desert, heathland, temperate grassland, temperate broadlead and northen coniferous forest, tundra\high mountains, polar ice 

aquatic biome

chracterised by physical and chemical environment, fresh and salt water, often stratified or zoned (zonation based on water depth, temp, proximity to shore etc).

global aquatic biomes

• Lakes 

• Streams abd rivers 

• Wetlands 

• Estuaries 

• Intertidal zone 

• Ocean pelagic zone 

• Marine benthic zone  

• coral reef 

oligotrophic vs eutrophic

oligotrophic= nutrient poor and oxygen rich

eutrophic= nutrient rich and oxygen poor

Species distribution

• Interactions between organisms and the environment limit the distribution of species 

Depends on:

• Dispersal 

• Biotic factors 

• Abiotic factors 

mechanisms of dispersal

wind

biotic factors (predation, herbivory, parasitism, competition)

abiotic factors (Temp, Water and humidity, Soil nutrients, Sunlight, Fire, Salinity, O2 (aquatic ecosystems) 

Temporal and spatial variability in these factors are often important 

Collective behaviour

• Self-emerging properties of individual organisms working together as a group 

• Group-level behaviour emerges from local interactions between individuals without central control (eg bird flocks, fish schools, human crowds etc) 

• Lead to new levels in biological organisation and new units of selection 

• Previously independent entities form a cooperative group (eg single cell multicellular organism 

• Lower level entities lose the ability to replicate alone 

Superorginism

group of synergistically interacting organisms of the same species 

Ethology: tinbergens 4 questions

Proximate causes 

• What causes the behaviour to be performed (eg Sensory inout from surrounding birds, neural processing, hormonal state, environmental triggers (eg predators) 

• How has the behaviour developed during the lifetime of the individual (eg learning of flocking behaviour, flight practice, neural plasticity/development)

Ultimate causes 

• How did the behaviour evolve (eg related species may show various levels of flock behaviour, likely built on ancestral behaviour (eg group roosting) 

• Why is the animal performing this behaviour (eg predator avoidance, foraging efficiency, aerodynamic benefits

Bird flocks/murmurations 

• Three individual simple rules lead to complex group-level behaviour 

1. Seperation: dont be too close to a neighbour 

2. Cohesion: move towards average position of your neighbour 

3. Alignment: adjust your velocity to average velocity of your neighbour 

Collective decision making

Not all individuals in the group have the same information available to them. Informed individuals can influence collective decision, even if they are well outnumbered by uninformed individuals 

 

Sociality in animals 

Sociality is a spectrum: solitary, subsocial, communal, quasisocial 

• Eusociality is defined by three traits 

1. Division of labour, with a caste system involving sterile individuals 

2. Co-operation among colony members in tending young 

3. Overlap of generations capable of contributing to colony function 

Division of labour (polyethism) 

age polyethism

• Young individuals take care of inside tasks: nursing larvae, cleaning

• Older individuals are dedicated to outside tasks: nest guarding, foraging

Worker caste differentiation

• In complex insect societies, worker can exhibit caste polymorphism

• Trophogenic caste differentiation: same genes, nutrition-dependent ontogeny

stigmergy

a form of self-organisation through indirect coordination and stereotyped behaviours

communication within superorganisms

pheromones play crucial role in organisation of insect societies (eg alarm pheromone, queen pheromone, orientation pheromone, trail pheromone etc)

eg Argentine ants can form super colonies and spread across continents

Shark evolution and diversity: 

• 12 living orders ~1150 species 

• Early forms in silurian (~400 million years ago) modern forms in jurassic (~144 mya)

• Found in coastal seas, open oceans, deep water, shallow water, benthic habittat 

• Range from small to large 

top predators that play important role in ecosystem promoting and indicating overall ecosystem health

Shark features and functional roles

• Protrusible jaws 

• Hyostylic jaw suspension 

• Top jaw detached from skull 

• Replacing distension 

• Smooth in one direction, rough in the other 

• Detect vibrations in water via sense of distant touch 

•  Lateral line 

• neuromasts with cilia

• Detect bioelectrical fields (electroreception) 

• Using ampullae of lorenzini 

roles include removal of sick/dying individuals and invaders, nutrient cycling and dispersal, fear induced behaviors and control)

threats to sharks

habitat loss and climate change, fishing and bycatch, culling

population ecology

• Population: a group of organism of the same species living in the same area, capable of interbreeding and sharing a gene pool 

• Population ecology focuses on factors affecting population size over time 

• The boundaries of a population are usually defined 

measuring population ecology: Density

(The number of individuals per area/volume)

Births and immigration increase population, deaths and emigration decrease popualtion 

How can we estimate? 

Count all individuals 

• Expensive and difficult, but there are some exceptions (eg kakapo w/ 244 birds) 

• Can also for sessile organisms 

Sample – plots of transects 

• Use a quadrat to standadise area sampled along a tape measure 

• Subsample an area and extrapolate 

• Eg cockle density estimates at pauatahanui 

Indirect sampling 

• Calls, dropping, nests, or tracks 

• Eg starlings roosting at lake serpentine 

Mark-recapture methods 

• Suitable for highly mobile and cryptic species 

• Capture, “mark”, and release 

• Allow individuals to mix back into the population 

• Capture a second sample and record number of marked individuals 

• Use N=sn/x where s is original sample size, n is second sample size, x is number of ducks from second sample already tagged, N is use to get population size estimate  

Population growth rate

Exponential growth: J shape, just gets growing, occurs under ideal conditions (plenty of resources). dN/dt=rN, or the population change depends on how big the population and growth rate are.

Logistic growth: S shape, eventually growth hits a flat point as exponetial growth cannot be sustained, occurs under realistic conditions, limited by carrying capacity (max population environment can support, K). dN/dt=rN((K-N)/K) or the population change depends on population size, growth rate, and how close the population is to carrying capacity

Population regulation

density dependent and independent processes influence final population sizes

Density dependent: effect on birth or death rate varies with population density (eg resource competition, territoriality, disease, intrinsic factors, toxic wastes)

density independent: effect on birth or death rate does not vary with population density (eg fire, volcanic eruptions, weather events, pollution)

Population dynamics

How stable are populations, and what causes them to fluctuate in size?

can occur at

irregular intervals (no patterns) (eg moose and wolf on isle royale, random)

regular cycle (eg snowshoe hare and lynx, when one rises other declines)

Dispersion

The pattern of spacing among individuals within the population 

• Clumped – most common (clump around ideal conditions) 

• Uniform – strong interactions between individuals (territorial, animals want space) 

• Random -  more uniform environments (no attraction towards area, no repulsion away from area) 

Life history traits

An organism's life history traits comprise the traits that affect its schedule of reproduction and survival. Life history traits are observable characteristics of the development, physiology, and behaviour of an organism to survival and reproduction 

Entails three components 

• The age of first reproduction (how soon should it reproduce) (Kauri tree at age 20-40, pine tree at age 6-13)

• How often the organism reproduces (Semelparity (reproduce once then die), Iteroparity (Repeated reproduction))

• How many offspring are produced per reproductive episode (Many offspring, low investment per individual, Few offspring, high investment per individual)

Biological community

A biological community is an assemblage of populations of various species living close enough for potential interaction

competition

A -/- interaction that occurs when individuals of different species both use a resource that limits the survival and reproduction of each species

Ecological niche

An ecological niche is the sum of an organism’s use of biotic and abiotic resources.

Competitive exclusion

Ecologically similar species can only coexist in a community if there are one or more significant differences in their niches

Resource partitioning

The division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting species. eg temporal partitioning (diurnal vs nocturnal)

Fundamental vs realised niche

A species’ fundamental niche is the niche potentially occupied by that species. A species’ realised niche is the niche actually occupied by that species.

As a result of competition, a species’ fundamental niche may differ from its realised niche

Character displacement

Character displacement is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species

– i.e. similar species in the same area look different

Community interactions

Interspecific interactions (between species) affect the survival and reproduction of the species that engage with them. (eg competition, facilitation, predation, mutualism, herbivory, commensalism, parasitism)

Resource exploitation

Exploitation refers to any +/– interaction in which one species benefits by feeding on the other species (+ denotes the winner (benefits), – denotes the loser)

Includes predation (+/–) and herbivory (+/–)

Predation

Predation (+/– interaction) refers to an interaction in which one species, the predator, kills and eats the other, the prey. • Predators have adaptations that enable them to find, identify, catch, and subdue their prey • For example, claws, fangs, or poison

Prey display various adaptations to avoid being eaten (– Behavioural defences include hiding, fleeing, and forming herds or schools, or morphological and physiological (mechanical or chemical) defence adaptations)

Camouflage and mimicry

• Aposematic colouration (warning colouration/bright colours) 

• Cryptic colouration (camoflague) 

• Batesian mimicry (a harmless species mimics a harmful one) 

• Mullarian mimicry (two unpalatable species mimic each other) 

Herbivory

Herbivory (+/– interaction) refers to an interaction in which a herbivore eats parts of a plant or algae. • Large mammals are the most familiar herbivores, but most herbivores are invertebrates. herbivores may have specialised adaptations.

Plants may produce toxic or distasteful chemicals, or mechanical defenses such as spines or thorns

Parasitism

Parasites derive their nutrition from another organism (host) and significantly affect survival and reproduction of the host.

• Endoparasites live within the body of the host.

• Ectoparasites live on the external surface of the host.

• Parasitoid insects lay eggs on living hosts and the larvae feed on the body of the host eventually killing it.

Mutualism

Mutualistic symbiosis (or mutualism) benefits both species (+ / +). Co-evolution typically causes related adaptations in both species – Change in one species is likely to affect change in the other

Commensalism

Commensalism benefits one species but neither harms nor helps the other (+ / 0). These are difficult to categorically prove in nature.

Facilitation

Facilitation = species have positive or negative affects without being in direct contact with other organisms (i.e. symbiosis). Facilitation is important in plant biology

Species with large impact

Certain species have a large impact on community structure due to their abundance or their role in community dynamics. dominant species, keystone species, ecosystem engineers

Ecosystem engineers 

Influence communities by changing the physical environment. Eg termites modify soils and allow nutrients to cycle 

keystone species

Have disproportionally large effects on community structure relative to biomass, ‘tiny but mighty’. Eg sea stars predate on mussels. with sea stars, communities were more diverse

dominant species

Species that are most abundant or; Have the highest biomass. Eg mangroves due to adaptation causing extreme tolerance for salt, specialised breathing roots, and ability to stabilise mudflats.

Factors affecting community diversity

Biogeography (latitude): Latitude affects the species diversity of biological communities.• Species richness is especially great in the tropics and generally declines in a gradient toward the poles, as Tropical environments have had more time for speciation to occur – older ecosystems while Temperate and polar communities have “started over” repeatedly following glaciations – repeated disturbance, younger ecosystems.

Pathogens: Disease-carrying microorganisms, viruses, viroid's (RNA molecules) or prions (proteins). eg kill coral which provides habitat for other animals.

Ecosystem Ecology

An ecosystem is the community of organisms in an area and the physical factors with which those organisms interact. ranges from a microcosm, eg under a fallen log, to a large area, eg a lake or island.

• Ecosystem ecology emphasises energy flow and chemical cycling between organisms and the environment. Abiotic and biotic components are critical for an ecosystem’s structure as their interactions allow energy to flow and nutrients to cycle. energy flows but nutrients cycle.

Producers (autotroph)

Primary producers= organisms that produce their own food via photosynthesis (sunlight convert inorganic matter to organic matter). Primary production=amount of light energy that is converted to chemical energy within a given time frame 

Consumers (heterotroph) 

Organism that rely on producers or other consumers as food 

Physical laws govern energy flow

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed. The second law of thermodynamics states that every exchange of energy increases the entropy of the universe. Energy enters an ecosystem as solar radiation and is lost from organisms as heat (inefficient energy conversions). Must be a constant source of energy (sun, geothermal)

Energy transfer

Amount of food converted to a consumer’s biomass is called secondary production. (assimilated energy for respiration and growth/development, non-assimilated energy for waste)

Trophic efficiency and ecological pyramids

Energy transfer between trophic level is typically ~10%.• Trophic efficiencies range from 5-20%.• 90% of the energy available at one level is NOT transferred to the next level

so for 1000000J sunlight, 10000J primary producers, 1000J primary consumers, 100 secondary consumers, 10J tertiary consumers.

Trophic structure and food webs

Trophic structure is the feeding relationships between organisms in a community. • Food chains link trophic levels from producers to top carnivores. The position an organism occupies in a food chain is called its trophic level.

Limits on food chain length

Each food chain in a food web is usually only a few links long. The energetic hypothesis suggests that length is limited by inefficient energy transfer. (Only about 10% of the energy stored in organic matter at each trophic level is converted to organic matter at the next trophic level). eg a producer level consisting of 100 kg of plant material can support about 10 kg of herbivore biomass and 1 kg of carnivore biomass.

Cycles of nutrients and water

Biological and geochemical processes cycle nutrients and water in ecosystems

• Some cycles include:

– The water cycle

– The carbon cycle

– The nitrogen cycle

– The phosphorus cycle

The nitrogen cycle

1. Nitrogen fixation: Atmospheric nitrogen gas (N²) is converted into ammonia (NH3) and ammonium ions (NH4+) by bacteria.

2. Nitrification: Ammonium ions (NH4+) are converted into nitrite (NO2 -) and then into nitrate (NO3 -) by soil bacteria.

3. Assimilation: Plants absorb nitrate (NO3 -) & animals eat plants

4. Ammonification: Plants and animals die, releasing ammonia (NH3) to soil. Bacteria convert to nitrate (NO3-)

5. Denitrification: Bacteria convert nitrate (NO3 -) to nitrogen gas (N²) in atmosphere

Restoration ecology

Restoration ecology = the scientific method for restoring degraded ecosystems through human intervention. A specialized conservation action aimed at returning ecosystems to their (semi-)natural state.

Freshwater Restoration Ecology

MCI = Macroinvertebrate Community Index. Traditionally, stream quality or “health” assessments were based on analysing water quality and focused on chemical data, but that only reflects conditions at time of sample. macroinvertebrates (MCI) capture influence of ecological stressors through time. High number = sensitive species, Low number = tolerant species. Scores indicate health of stream:MCI > 100 = clean water, MCI < 80 = polluted. eg project twin streams engage west Auckland communities with local streams restoration

conservation biology

Conservation biology is a scientific field that has developed in response to the challenge of preserving species and ecosystems. focuses on biodiversity, goal is document full range of biodiversity on earth.

Human activities add to natural disturbances (change trophic structures, energy flow, and chemical cycling). Conservation biology aims to understand the role of human and natural disturbances on species & ecosystems processes

Biodiversity

genetic: the genetic variation found within each species

species: the range of species within an ecosystem

community: the variety of habitat types and ecosystem processes extending over a given region

Species diversity in NZ

fairy tern. Degradation of breeding habitat – dune stabilisation.

• Predation (gulls, introduced mammals).

• Extreme environmental events.

• Disturbance by humans during the breeding season

• Infertility

Extinction vortex (genetic diversity in nz)

Extinction vortex driven by low genetic variation (small population → inbreeding, genetic drift → loss of genetic variability → lower individual fitness and popualtion adaptibilty → lower reproduction, higher mortality → smaller population)

Small populations are particularly vulnerable to overharvesting, habitat loss, and other threats.

eg Little spotted kiwi have the lowest genetic diversity out of all kiwi species and are vulnerable to disease and environmental stressors

Community diversity in NZ

Dactylanthus taylorii is New Zealand's only indigenous fully parasitic flowering plant – grows underground attached to tree roots.

• Dactylanthus flowers are adapted for pollination by short-tailed bats, but in serious decline due to rats eating flowers and declines in short tailed bats

Threats to biodiversity

global change, habitat loss, overharvesting, invasive species. Humans have physically altered nearly half of Earth’s land surface. • Human activities pose threats at local, regional and global scales and are rapidly pushing many species toward extinction.

Habitat loss

Habitat loss occurs due to agriculture, urban development, forestry, mining, pollution. Habitat loss is a factor for 73% of species that have become extinct, endangered, vulnerable or rare in the last few hundred years. eg deforestation in vietnam due to agent orange (vietnam war) and agricultural practises (food insecurity).

overharvesting

Overharvesting especially affects:

– Species with restricted habitats (e.g. small islands) (great auk)

– Large organisms with low reproductive rates (elephants - ivory trade)

– Commercially valuable species (southern bluefin tuna)

Global changes

Global change includes:

– Altering climate

– Changes to atmospheric chemistry (acid rain)

– Affecting ecological systems that reduce earth’s capacity to sustain life

invasive species

species that occur outside their natural ranges spread and increase in numbers occur at the expense of native species. create Competition (zebra mussel), Ecosystem modification (algae), Predation (brown tree snake).

NZ Case study on threats

Vulnerable traits of native birds:

– Evolved in isolation

– Antipredator response is to freeze

– Ground nesting, often flightless

– Evolved to avoid avian predators (Dull coloured, Strongly scented)

Successful traits of invasive mammals:

– Nocturnal mammals (available niche)

– Scent orientated

– Adept climbers

– Neophobic

Specific impacts of invasive species in NZ:

Competition (rodents - ship rats, norway rats, house mouse)

Ecosystem modification (brushtail possum)

Predation (mustelids - stoats and ferrets)

Sustaining biodiversity

Critically endangered species require individual attention. Modern conservation efforts aimed to sustain the biodiversity of entire communities, ecosystems, and landscapes. Habitat loss → Reconnect fragmented habitat (Artificial corridors can improve connectivity) or establishing protected areas (predator free islands), urban restoration

Invasive species managment

1. Keep pests out! (NZ biosecurity at ports)

2. Eradicate (easiest on islands)

• Sufficient resources to eliminate

• Minimise reinvasion

3. Sustained control (traps)

• Physical

• Chemical