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Animal And Plant Ecology > Semester 2 > Flashcards

Semester 2 Flashcards

1
Q

What are the 5 concepts of ecology?

A
  1. Ecological systems exist in a hierarchical organisation
  2. Ecological systems are governed by physical and biological principles
  3. Different roles organisms play in ecological systems
  4. Scientists use several approaches to studying ecology
  5. Humans influence ecological systems
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2
Q

What is ecology?

A

Study of how organisms interact with

Very broad topic

Various levels - individual to global

Helps us understand how the world works

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3
Q

What are ecological systems?

A

Biological entities that have their own internal processes and interact with their external surroundings

Population: population dynamics > ten unit of evolution

Individual: survival and reproduction > the unit of natural selection

Community: interactions among species

Ecosystem: flow of energy and matter

Biosphere - global processes

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4
Q

What is a species?

A

A group of organisms that can reproduce naturally with one another and create FERTILE offspring

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5
Q

Studying ecology at different levels

A

Individual approach: understands how adaptations or characteristics of an individuals behaviour, morphology and physiology enable it to survive in an environment

Population approach: examines variation in the number, density and composition of individuals over time and space

Community approach: understands the diversity and interactions of organisms living together in the same place

Ecosystem approach: describes the storage and transfer of energy and matter

Biosphere approach: examines the movements of energy and chemicals over the earths surface

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6
Q

What are the governing principles of ecology?

A

First law of thermodynamics - matter and energy cannot be created or destroyed but can change form (law of conservation of matter)

A dynamic steady state - occurs when gains and losses are in balance. Behaviour affects ecology

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7
Q

What is natural selection?

A

Differential survival and reproduction of individuals that possess certain phenotypes

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8
Q

What is evolution?

A

A change in the frequency of genes / characteristics in a population over generations

Individuals with better fitness will pass more copies of their genes to the next generation and that phenotype will come to dominate

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9
Q

Types of species interactions

A

Interactions that provide a benefit to a species are indicated by a ‘+’ symbol

Interactions that cause harm to a species are indicated by ‘-‘ symbol

Interactions that have NO effect on a species are indicated by a ‘0’ symbol

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10
Q

What is a habitat ?

A

The place or physical setting where an organism lives.

Distinguished by physical features such as dominant plant type

Habitat types overlap and absolute distinctions rarely exist

Examples:
Freshwater, marine, coastal, streams, forests, deserts, grasslands

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11
Q

Habitats and niches

A

Unique phenotypes: if not then extinction of a species!

Example: different insects like to feed on different crop species that may be growing in the same field

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12
Q

The scientific method

A

Hypotheses: ideas that potentially explain a repeated observation

Proximate hypotheses ‘how’: address the cause of immediate changes in individual phenotypes or interactions

Ultimate hypotheses ‘why’: address the fitness costs and benefits of a response. Behavioural ecology

Predictions: statements that arise logically from hypotheses

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13
Q

Manipulative experiments

A

Where a hypotheses is tested by altering factor hypothesised to be the cause of a phenomenon

Treatment: the factor that we want to manipulate in a study

Control: a treatment that includes all aspects of an experiment except the factor of interest

Example - researchers want to test if birds are an important factor in determining the number of insects on oak trees. They manipulate the presence of birds by placing cages around oak trees. Some trees were left uncaged as controls

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14
Q

Manipulative experiments

A

Experimental unit: the object to which we apply a manipulation

Replication: being able to produce a similar outcome multiple times (ie the number of experimental units per treatment)

Randomisation: a requirement for manipulation experiments, every experimental unit must have an equal chance of being assigned to a particular treatment

Experimental units may be natural (lakes) or artificial (microcosms) and may vary in size by several orders of magnitude

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15
Q

Alternative types of experiments

A

Natural experiments: an approach to hypothesis testing that relies on natural variation in the environment to test a hypothesis

Mathematical methods: representations of a system with a set of equations that correspond to hypothesised relationships among the systems components

Ecologists often test mathematic models using natural or manipulative experiments

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16
Q

What is the impact of humans as a species

A

8 billion - 15 November 2022 was predicted to be the day that the global population reaches 8 billion

Each year 78 million + added, greater than population of UK and 2x Ireland combined

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17
Q

How do humans influence everything

A

2% of remaining primary rain forest lost per year

50% of usable land used for agriculture

Semi arid subtropical regions turned to desert by overgrazing and firewood collection

Majority of fish stocks have collapsed

Climate change resulting from fossil fuel use

Humans use 20% more renewables than are actually renewed

6th great extinction

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18
Q

Passenger pigeon

A

Perhaps one of the greatest declines in population size

6 billion to none in 100 years, last died in 1914

The Allee effect - unpredicted effect of low densities

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19
Q

Terrestrial biomes

A

Are categorised by their major plant growth forms

Biomes > classified based on temperature and rainfall

Cold, wet are rare

There is often an association between the plant forms in a biome and the animal forms that live there

Boundaries between biomes can be unclear

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20
Q

Terrestrial biomes

A

There are 9 biomes within 3 temp ranges:

<5 degrees
5 degrees - 20 degrees
> 20 degrees

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21
Q

Climate diagrams

A

Graphs that plot the average monthly temperature and precipitation of a specific location on earth

Growing season > months that are warm enough to allow plant growth ie temps > 0 degrees > shaded regions in diagram

Plant growth is constrained by temperature

When precipitation line is ABOVE temp line, plant growth is limited by temp.
When line is BELOW temp line, plant growth is LIMITED by precipitation

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22
Q

Terrestrial biomes

A

There are 9 categories of terrestrial biomes

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23
Q

Tundras

A

The COLDEST biome, treeless expanse above permanently frozen soil (permafrost)

Upper soils thaw during brief summer growing season

Dry > precipitation is < 600mm

Extreme tolerators > soils are acidic and nutrient poor

Plants grow low to the ground to gain protection under snow and ice

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24
Q

Boreal forests

A

Dominated by evergreen needle leaves trees with a short growing season and severe winters

Temps are <5 degrees and low rainfall

Litter decomposes slowly and accumulated forming the LARGEST reservoir of organic carbon on earth

Soils are acidic and podsolised

Species diversity is LOW but the biome is a major source of timber and paper

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25
Q

Temperate rainforests

A

A biome known for mild temperatures and abundant precipitation and dominated by evergreen forests

Warmer conditions are due to nearby warm ocean currents

These forests typically support low species diversity

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26
Q

Temperate seasonal rainforests

A

A biome with moderate temp and precipitation conditions, dominated by deciduous trees eg maple, beech, oak

Conditions fluctuate because forests are NOT near warm ocean currents

Precipitation exceeds transpiration

Soils are podsolised, slightly acidic and support a layer of small plants beneath the dominant trees

Warmer and drier parts of the biome are dominated by pines

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27
Q

Woodlands / Shrub lands

A

A biome characterised by hot, dry summers and mild, wet winters

Combination that favours the growth of drought tolerant grasses and shrubs

There is a 12 month growing season but dry summers, cold winters and frequent fires limit plant growth

Dominated by Schlerophyllous vegetation which had small durable leaves that resist dessication

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28
Q

Temperate grasslands / cold deserts

A

A biome characterised by hot, dry summers and cold winters

Dominated by grasses, non woody flowering plants and drought adapted shrubs

Soils nutrient rich with lots of organic matter

Unproductive, cold deserts occur when precipitation <250mm

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29
Q

Tropical rainforests

A

A warm and Rainy (at least 2000mm annually) biome with multiple layers of lush vegetation

There is a canopy of 30-40 m trees with an understory containing smaller trees, shrubs, epiphytes and vines

Species diversity is higher than anywhere else in the world!

Organic matter decomposes quickly and vegetation rapidly takes up nutrients

Soils are devoid of humus and clay and retain nutrients very poorly

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30
Q

Tropical seasonal forests / Savannas

A

A biome with warm temps and pronounced wet and dry seasons > due to movement of the inter tropical convergence zone

Dominated by deciduous trees that shed leaves during the dry season

Savannas have long dry periods and contain grasses and occasional trees

Fire and grazing Maintain Savannas

Soils do NOT hold nutrients but the warm climate favours rapid decomposition and fast growth

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31
Q

Sub tropical deserts

A

A biome characterised by hot temps, scarce rainfall, long growing seasons and sparse vegetation

Soils are shallow and devoid of organic matter and neutral ph

Moister sites support succulent cacti, shrubs and small trees eg mesquite and paloverde

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32
Q

Global wind circulation

A

Inter tropical convergence zone

1> Hadley cell
2> Ferrel cell
3> polar cell

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33
Q

Aquatic biomes

A

Categorised by their flow, depth and salinity

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34
Q

Streams and rivers

A

Lotic > refers to flowing water systems

Stream support fewer species than other aquatic biomes

Small streams are limited in primary productivity > why?

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35
Q

Streams and rivers

A

Riparian zone > terrestrial vegetation alongside rivers and streams that is influenced by seasonal flooding and elevated water tables

Allochthonous > inputs of organic matter such as leaves that come from outside of an ecosystem (ie from a riparian zone)

Autochthonous > inputs of organic matter that are produced by algae and aquatic plants inside an ecosystem

Much of organic matter in streams is allochthonous (introduced) and rivers is autochthonous

Rivers typically accumulate sediments from land and high turbidity can block light and reduce primary production

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36
Q

Influence of dams

A

Dams are built to control flooding, produce water for irrigation or to generate electricity

Dams alter seasonal cycles of flooding and disrupt the natural movement of aquatic organisms upstream and down stream

Flooding also impacts terrestrial biodiversity

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37
Q

Ponds and lakes

A

Pond > aquatic biome that is smaller than a lake and is characterised by NON flowing fresh water with some area of water that is too deep for plants to rise above the waters surface

Lake > an aquatic biome that is LARGER than a pond and is characterised by NON flowing fresh water with some areas of water that is too deep for plants to rise above

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38
Q

Circulation in ponds and lakes > seasonal temps alter water density, water becomes more dense as it cools to 4 degrees and LESS dense as it cools below 4 degrees

A

As surface waters continue to warm during the summer, they gain heat faster than deeper waters and float on the surface

As surface waters cool during autumn they begin to sink

During the winter water less than 4 degrees floats beneath the ice

As surface waters warm during the spring, nutrients on bottom and oxygen on top are cycled

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39
Q

Freshwater wetlands

A

An aquatic biome containing standing fresh water or soils saturated with fresh water for at least part of the year, shallow enough for emergent vegetation throughout all depths

Wetlands provide > animal habitat > important natural purification systems

Swamps contain emergent trees

Marshes contain emergent NON woody vegetation

Bogs contain acidic water and plants adapted to these conditions

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40
Q

Salt marshes / estuaries

A

Salt marshes > a saltwater biome that contains NON woody emergent vegetation

Salt marshes are often found at continental coasts and in estuaries where the mouths of rivers mix with salt water from oceans

Estuaries contain abundant nutrients and sediments carried downstream by rivers

This supports extremely high biological productivity

Estuaries are often surrounded by tidal marshes which are some of the most productive habitats on earth

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41
Q

Mangrove swamps

A

A biome that occurs along tropical and sub tropical coasts and contains salt tolerant trees with roots submerged in water

Salt tolerance is key adaptation of trees in mangrove swamps

Mangrove trees prevent the erosion of shorelines from incoming waves

They provide habitat for many species of fish and shellfish

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42
Q

Inter tidal zones

A

A biome consisting of the narrow band of coastline between the levels of high tide and low tide

As the tide comes and goes, water exhibits widely fluctuating temps and salt concentrations

Can occur in a variety of areas from rocky coastlines to sloping mudflats

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43
Q

Coral reefs

A

A marine biome found in warm, shallow waters that are 20 degrees year round

Recent discovery > pristine coral reef 30m (twilight zone) off Tahiti > Nov 2021.

Corals are tiny animals in a mutualistic relationship with algae, corals produce co2 and algae produce sugars

They are hollow tubes with exo skeletons and tentacles that collect detritus and plankton

Corals live in colonies > their exo skeleton contributes to the structure of reefs

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44
Q

Corals reefs - reversing the damage

A

Rising temps is causing coral bleaching

Hong Kong > artificial reefs 2002

Using sound to repopulate reefs

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45
Q

Life history concepts

A

Life history traits represent the schedule of an organisms life

Life history traits are shaped by trade offs

Organisms differ in the number of times that they reproduce but they all eventually become senescent

Life histories are sensitive to environmental conditions

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46
Q

Life history

A

The schedule of an organisms growth, development, reproduction and survival > represents an allocation of limited time and resources to achieve maximum reproductive success

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47
Q

Slow to fast continuum

A

Variation in one life history trait is often correlated with variation in other life history traits eg. The number of offspring is negatively correlated with the size of offspring

Slow life history > long time to sexual maturity, low numbers of offspring, high parental investment

Fast life history > short time to sexual maturity, high numbers of offspring, little parental investment

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48
Q

Life history traits in plants

A

Conceptual model> J Philip grime proposed that plant life history depends on stress, competition and the frequency of disturbances

Plants functioning at the extremes of these environmental axes could be categorised as stress tolerators, competitors or ruderals

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49
Q

Life history traits in plants

A

Stress tolerators eg. Woody lousewort > typically small herbs with a long life span, slow growth and a long time to sexual maturity

Many stress tolerators rely on vegetative reproduction (reproducing from roots and stems) instead of producing costly seeds

Competitors eg. Goldenrod > when conditions are less stressful, grow fast, achieve early sexual maturity and devote little energy to seed production

Ruderals (eg. Weeds such as thistle) grow fast and devote a high proportion of their energy to seed reproduction

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50
Q

The principle of allocation

A

NO organism possesses the best of all life history traits

Principle of allocation > when resources are devoted to one body structure, physiological function or behaviour they cannot be allotted to another

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51
Q

Trade offs

A

Organisms face trade offs, when one life history trait is favoured and it prevents the adoption of other advantageous traits
Eg. Trade off between offspring number and offspring survival

Natural selection will favour individuals that allocate their resources in a way that achieves maximum fitness

Optimised life history resolves conflicts between competing demands of survival and reproduction to achieve maximum fitness

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52
Q

Offspring number vs size

A

Most organisms face a trade off between the number of offspring they can produce and the size of those offspring

The expected trade off is often not observed.
For many organisms the number of offspring can be variable but the size remains relatively constant why?

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53
Q

Offspring number vs parental care

A

As the number of offspring increases, the parental care per offspring decreases, reducing chances of offspring survival

Depends on environmental conditions eg. Number of daylight hours that parents have to find resources for their offspring

Test for this trade off > manipulate the number of offspring that a parent has

Example: removal of eggs from a magpies nest results in fewer total offspring

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54
Q

Parental care vs parental survival

A

Having more offspring can stimulate parents to hunt harder for food to feed their offspring

This additional effort can affect the parents fitness

Example: researchers added or removed 2 chicks or did NOT change (control) the number of kestrel eggs.
Removal and control nests > 98% of chicks survived. Chicks in enlarged broods > 81% survived.

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55
Q

Growth rate vs fitness

A

Allocation of energy to increased fecundity during one year occurs at the cost of further growth that year

Determinate growth > a growth pattern in which an individual does NOT grow any more once it initiates reproduction
Occurs in many species of birds and mammals ie. Should favour long life span organisms

Indeterminate growth - should favour short life span organisms

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56
Q

Growth rate vs fitness

A

Delaying sexual maturity allows an individual to grow large and produce more offspring per year once reproduction starts

Comparing across many species (within taxonomic groups):
The age of sexual maturity is positively associated with the number of years an animal will survive after reaching sexual maturity

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57
Q

Trade offs of Trinidadian guppies

A

The Trinidian guppy is common in the streams of Trinidad

In lower streams > guppies have short life expectancies, predation by pike cichlids and kill fish = high predation risk

In higher elevation streams > guppies have long life expectancies, predator free = low predation risk

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58
Q

Senescence

A

A gradual decrease in fecundity and body condition and an increase in the probability of mortality

Example:
Between the ages of 30 and 85, the rates of human metabolism, nerve conduction, blood circulation and breathing capacity decrease up to 65%. Over time, the function of the immune system also declines leading to higher death rates

Organisms differ in the number of times they reproduce before senescence

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59
Q

Semelparity

A

Arises when there is a massive amount of energy required for reproduction

Examples:
Bamboos, agaves, some octopus, cicadas

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60
Q

Semelparity and iteroparity

A

Examples:
Yuccas are mostly iteroparous (multiple) but some varieties are Semelparous (single)

Differences in breeding patterns lead to trade offs in flower and fruit numbers and in germination rates

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61
Q

Why does senescence exist?

A

Senescence is an inevitable consequence of natural wear and tear and may be the accumulation of molecular defects that fail to be repaired eg. From ultraviolet radiation

Long lived animals appear to have better mechanisms for reducing the production of reactive forms of oxygen and repairing damaged DNA and protein molecules

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62
Q

Stimuli for change

A

The right timing of life history events is critical so behaviour and physiology match changing environmental conditions

Organisms rely on various indirect, environmental cues

Photoperiod > the amount of lift that occurs each day, provides a cue for many events in the life histories of virtually all organisms

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63
Q

The effect of resources

A

Fluctuations in resource availability often determines the timing of life history events

Example:
Like many amphibians, the barking tree frog undergoes metamorphosis

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64
Q

The effect of predation

A

Predation can affect many life history traits (eg. Time to and size at hatching, metamorphosis and sexual maturity)

Example: hatching and sexual maturity

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65
Q

The effects of global warming

A

Small changes in temp can have substantial impacts on an organisms physiological processes

The increase in global temp has changed the breeding times of many animals and plants

Example: North American tree swallows

Changes in temp can alter initiation of flower production

Example: Thoreau and others observed the time of first flower for more than 500 species of flowering plants in Concord, Massachusetts

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66
Q

Consequences of altered breeding

A

Problems can arise when a species depends on the environment to provide necessary resources with an altered breeding season

Example: the pied flycatcher breeds in Europe each spring

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67
Q

Impact of humans

A

In addition to global warming, human activities can impose strong selection and have substantial impacts on organisms life histories

Example:
Commercial fisheries impose selection pressure on fish size by harvesting only the largest individuals.
Between the 1930s and 1970s the average age at maturity of north east artic cod decreased to 7-9yrs
This shift is likely associated with changes in fecundity and longevity

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68
Q

Concepts of ecology - population distribution

A

The distribution of populations is limited to ecologically suitable habitats

Population distributions have 5 important characteristics

The distribution properties of populations can be estimated

Population abundance and density are related to geographic range and adult body size

Dispersal is essential to colonising new areas

Many populations live in distinct patches of habitat

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69
Q

Distributions of populations

A

Spatial structure > the pattern of density and spacing of individuals in a population

Small scale variation in the environment creates geographic ranges that are composed of small patches of suitable habitat
Example: the geographic range of Fremonts leather flower is just 3 countries in Missouri

It is possible to test whether species are limited by unsuitable environmental conditions

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70
Q

Ecological niche modelling

A

General rule > populations can increase in more suitable habitats
Understanding the realised niche of a species aids in species conservation and can help to limit the spread of invasive species

Ecological niche modelling > the process of determining the suitable habitat conditions for species

Ecological envelope > the range of ecological conditions that are predicted to be suitable for a species (differs from the realises niche which describes conditions in which a species currently exists)

Can use historic distributions of species of few individuals or extinct

71
Q

Modelling invasive species

A

Ecological niche modelling can predict the expansion of pest species

Example: the Chinese bushclover was taken to the US to control erosion, provide cattle feed and reclaim mined land

72
Q

Effects of global warming

A

During the past century, the average temp of the earth has increased by 0.8 degrees

Temp change can cause a shift in the geographic range of species

Warmer northern temps in the North Sea has caused southern fish species to expand their ranges northward

73
Q

Population characteristics

A

Geographic range > where is it found?

Abundance > the total number of individuals in a population within a defined area
Eg. Total number of lizards on a mountain

74
Q

Population density

A

If population density is greater than what the habitat can support, some individuals must leave or the population will experience lower growth and survival

Largest density of individuals often near the centre of a populations geographic range

75
Q

Population dispersion

A

Dispersion > the spacing of individuals with respect to one another within the geographic range of the population

76
Q

Population dispersal

A

Dispersal > the movement of individuals from one area to another

Dispersal is distinct from migration, which is the seasonal movement of individuals back and forth between habitats

It is the mechanism by which individuals can move between suitable habitats

Dispersal allows species to colonise areas outside of their geographic ranges

77
Q

Quantifying individuals

A

Area and volume based surveys > surveys that define the boundaries of an area or volume and then count all of the individuals in the space

The size of the defined space is related to the abundance and density of the population

By taking multiple samples, it is possible to determine how many individuals are in an average sample

Line transect surveys > surveys that count the number of individuals observed as one moves along a line. This data can be converted into area estimates of a population

78
Q

Quantifying individuals

A

Many animals are sensitive to the presence of researchers and will leave the area when surveyed.

Other species are camouflaged and may be difficult to find.

Mark recapture survey > a method of population estimation in which researchers capture and mark a subset of a population from an area, return it to the area and capture a second sample of the population after time has passed

79
Q

Population size is estimated by assuming that:

A

Initially captured individuals (M) divided by population size (N)

=

Marked recapture individuals (R) divided by total individuals captured in 2nd sample (C)

80
Q

Quantifying dispersal

A

Dispersal can be quantified by measuring how far individuals travel from where they were marked
Eg. With ear tags, radio transmitters, leg bands

Lifetime dispersal distance > the average distance an individual moves from where it was born to where it reproduces

This provides an estimate for how fast a population can increase its geographic range

81
Q

Quantifying dispersal

A

Dispersal can cause a geographic range to expand rapidly if a few individuals can disperse much farther than the average individual

Example: by marking different species of songbirds with rings

82
Q

Population abundance and range

A

Populations with high abundance also have large geographic ranges

This pattern has been observed for many organisms (eg. Birds)

83
Q

Population density and body size

A

The density of a population is negatively correlated to the body size of the species

84
Q

Dispersal limitation

A

The absence of a population from suitable habitat because of barriers to dispersal

85
Q

Habitat corridors

A

A strip of favourable habitat located between 2 large patches of habitat that facilitates dispersal eg. A narrow band of trees that connects forests

Conservation efforts have increasingly considered the preservation of corridor habitats

Example: biologists have pushed to protect riverside habitats along the Rio Grande that would allow species to move easily among large patches of protected land

86
Q

The ideal free distribution

A

Whenever possible, individuals choose habitats that provide the most energy

As individuals move to high quality habitat, resource must be divided among more individuals ie. Reduced per capita benefit

Per capita benefit can fall so low that an individual would benefit by moving to low quality habitat!

Ideal free distribution > when individuals distribute themselves among different habitats in a way that allows them to have the same per capita benefit > assumes perfect knowledge of habitat variation

87
Q

The ideal free distribution example

A

Milinski 1979

Stickleback fish were distributed proportionally throughout an aquarium

Researchers manipulated the abundance of prey (water fleas) on each side of the aquarium such that one side had 1/5th the abundance of water fleas as the other side

88
Q

The ideal free distribution

A

Assumes perfect knowledge of habitat variation

Individuals may not be aware that other habitats exist

Individuals in nature rarely meet the expectations required by the ideal free distribution

Fitness is not solely determined by maximising resources, other factors may influence distribution such as the presence of predators or territory owners (despotic behaviour)

89
Q

Models of spatial structure

A

Sub populations > when a large population is broken up into smaller groups that live in isolated patches

If individuals frequently disperse among sub populations, all sub populations increase and decrease in abundance synchronously

If dispersal is infrequent, each sub population fluctuates independently

90
Q

Models of spatial structure

A

Basic meta population model > a model that describes a scenario in which there are:
Patches of suitable habitat embedded within a matrix of unsuitable habitat
All suitable patches are assumed to be of equal quality

Source sink meta population model > a population model that builds upon basic model and accounts for the fact that not all patches of suitable habitat are of equal quality

Source sub population > in high quality habitats they serve as a source of dispersers within a meta population

Sink sub population > in low quality habitats, they rely on outside dispersers to maintain the sub population within a meta population

91
Q

Models of spatial structure

A

Landscape metapopulation model > a population model that considers both differences in the quality of the suitable patches and the quality of the surrounding matrix (eg. Habitat corridors)

92
Q

Concepts of ecology - population growth

A
  1. Under ideal conditions, populations can grow rapidly
  2. Populations have growth limits
  3. Population growth is influenced by the proportions of individuals in different age, size and life history classes
93
Q

Population demography

A

Demography > the study of populations

Incorporates > birth rates and death rates, movement (dispersal), age structure and sex / gender ratios

Can be used to predict growth of a population

Not all individuals contribute equally to population growth

94
Q

Population dynamics

A

Births and immigration > adds individuals to the population

Deaths and emigration > removes individuals from a population

Change in population size = births + immigrants entering population - deaths - emigrants leaving population

95
Q

The population growth rate (per capita rate of increase / intrinsic growth rate) can be expressed mathematically:

A

Triangle N divided by triangle t = B - D

B is the number of births
D is the number of deaths
Triangle N is the change in population size
Triangle t is the time interval

Growth rate = B - D

96
Q

The per capita rate of increase (r) aka intrinsic growth rate is given by

A

Triangle N divided by triangle t = rN

97
Q

Exponential growth model

A

Exponential growth > population increase under ideal conditions

A model of population growth in which the population increases continuously at an exponential rate and can be described by the equation:

Nt = N0e ^ rt

Nt = future population size
N0 = current population size
r = intrinsic growth rate
t = time over which population grows
e = natural exponential > approx 2.71828

J shaped curve > the shape of exponential growth when graphed

98
Q

Exponential Growth model

A

Populations initially grow slowly because there is a small number of reproductive individuals, growth rate increases with the number of reproductive individuals

The rate of a populations growth at any point in time is the derivative of this equation:

Triangle N divided by triangle t = rN

Which means:

Change in population divided by change in time = intrinsic growth rate x population at a point

99
Q

Exponential growth ( J shaped curve)

A

The rate of increase is constant but the population accumulated more new individuals per unit time when it is large then when it is small

100
Q

Geometric growth model

A

A model of population growth that compares population sizes at regular time intervals (usually year)

It is expressed as a ratio of a populations size in one year to its size in the preceding year. It can NOT be less than 0

When it’s greater than 1, population size has increased

101
Q

Population doubling time

A

Doubling time > the time required for a population to double in size, can be estimated by rearranging the exponential growth model:

t = loge 2 divided by r

For the geometric model, the equation is nearly the same. Recall that r = logeŷ so we can replace r with logeŷ

t2 = loge 2 divided by loge upside down y

102
Q

Density independant

A

Factors that limit population size regardless of the populations density

103
Q

Density dependant

A

Factors that affect population size in relation to the populations density

Negative density dependence > when the rate of population growth decreases as population density increases

Limiting resources > ad population increases, resources are divided among more individuals. Per capita resources decline to a level at which individuals find it difficult to grow and reproduce

BUT Allee effect > reverse may be true of below threshold number

104
Q

The logistic growth model

A

Carrying capacity (k) > the maximum population size that can be supported by the environment

A growth model that describes slowing growth of populations at high densities

S shaped curve > the shape of the curve when a population is graphed over time using the logistic growth model

Inflection point > the point on a sigmoidal growth curve at which the population had its highest growth rate

105
Q

The logistic growth model

A

As the population increases from a very small size, the rate of increase grows until reaching 1/2 of the carrying capacity (Corresponding to the inflection point)

Individuals in the population continually decline in their ability to contribute to population growth

106
Q

Predicting human growth

A

The logistic growth model was formulated by Pierre Francois Verlhulst to describe human population growth in 1804

107
Q

Survivorship Curves

A

Type 1 > depicts a population that experiences low mortality early in life and high later in life

Type 2 > a pop that experiences constant mortality throughout its life span

Type 3 > a pop with high mortality early in life and high survival later in life

Most populations exhibit a curve that combines features of type 2 and 3

108
Q

Life tables

A

Age specific summary of the survival pattern of a population

They are typically based on the number of female offspring per female

Stable age distribution > when the age structure of a pop does NOT change over time, occurs when survival and fecundity of each age class stays constant over time

Survival rate > the probability of surviving from one age class to the next

Survivorship > probability of surviving from birth to any later age

109
Q

Collecting data for life table

A

Cohort life table > follows a group of individuals born at the same time from birth to death of the last individual

Environmental changes can affect the survival and fecundity of a cohort, it is difficult to separate the effects of age and the environment

Time specific / static life table > quantifies the survival and fecundity of all individuals in a pop during a single time interval
Age is not confounded with time, all subjected to same environmental conditions, not as time consuming

110
Q

Life tables

A

Net reproductive rate R0 > the total number of female offspring that we expect an average female to produce over the course of her life

Generation time T > the average time in years between the birth of an individual and the birth of its offspring

When upside down y or r is estimated from a life table, it is assumed that the life table has a STABLE age distribution

Age distributions fluctuate due to environmental conditions, so any approximation of upside down y or r is restricted to to the environmental conditions that the pop experiences at the time of measurement!

111
Q

Concepts for ecology - population distribution 2

A

Populations fluctuate naturally over time

Density dependence with time delays can cause populations to be inherently cyclic

Chance events can cause small populations to go extinct

Metapopualtions are composed of sub populations that can experience independent population dynamics across space

112
Q

Population fluctuations

A

All populations experience fluctuations due to factors such as availability of resources, predation, competition, disease, parasites and climate

Fluctuations include random and cyclic changes through time

Some populations tend to remain relatively stable over long periods

In contrast some populations exhibit much wider fluctuations:
Small organisms (eg. Algae) tend to reproduce fast and are not as buffered against starvation.
They have a high surface area to volume ratio so they maintain homeostasis

113
Q

Age structure variations

A

When an age group contains a high or low number of individuals the population likely experienced high birth or death rates in the past

Long term fluctuations in age structure can be determined for a forest by examining tree rings

114
Q

Overshoots and die offs

A

Populations in nature rarely follow a smooth approach to their carrying capacity

Overshoot > when a population grows beyond its carrying capacity

Die off > a substantial decline in density that typically goes well below the carrying capacity

115
Q

Cyclic population fluctuations

A

Population cycles > regular oscillation of a population over a longer period of time

Some populations can exhibit highly regular fluctuations in size

Cyclic populations can occur among related species and across large geographic areas (eg. The synchronous cycles of grouse in Finland)

116
Q

Cyclic behaviour of populations

A

Populations have inherent periodicity and tend to fluctuate up and down although the time required to complete a cycle differs among species

Populations are stable at their carrying capacity

If population size decreases, the population responds by growing and often overshooting carrying capacity

Overshoots can occur when there is a delay between the initiation of breeding and the time that offspring are added to the population

117
Q

Delayed density dependence

A

When density dependance occurs based on a population density at some time in the past

Eg. Moose breed in autumn

As the time delay increases, density dependence is delayed and the population is more prone to both overshooting and undershooting k

Damped oscillations > a pattern of pop growth where pop initially oscillates but the magnitude of the oscillations declines over time

Stable limit cycle > a pattern of pop growth in which the pop continues to exhibit large oscillations over time

118
Q

Cycles in laboratory populations

A

Delayed density dependence may occur because:

1) the organism can store energy and nutrient reserves

2) there is a time delay in development from one life stage to another

119
Q

Extinctions in small populations

A

Small populations are more vulnerable to extinction than larger populations

120
Q

Extinction due to growth rates

A

Data suggests that small populations are more likely to go extinct but growth models suggest that they should have more rapid growth and be resistant to extinction!

This contradiction can be resolved by incorporating random variation of growth rates into growth models

Deterministic model > designed to predict a result without accumulating for random variation in population growth rate

Stochastic model > incorporates random variation in pop growth rate and assumes that variation in birth and death rates is due to random chance

121
Q

Extinction due to growth rates

A

Demographic stochasticity > variation in birth rates and death rates due to random differences among individuals

Environmental stochasticity > variation in birth rates and death rates due to random changes in the environmental conditions eg. Changes in weather

Low birth / high death for a number of years > extinction is more likely

Increased chance of having a string of bad years over time

Smaller populations are at more risk of extinction if they experience a string of bad years

122
Q

Patchy habitats

A

Preferred habitat often occurs as patches of suitable habitat surrounded by a matrix or unsuitable habitat

Eg. A wetland

123
Q

Habitat fragmentation

A

The process of breaking up large habitats into a number of smaller habitats

Some habitat fragments experience extinctions, other colonised by dispersers

Sources are: high quality patches that produce large number of individuals that disperse to other patches

Sinks are > low quality patches that produce few individuals and rely on dispersers to keep the sink population from going extinct

Patch connectivity influences the abundance of sub populations

124
Q

Basic model of metapopualtions

A

Assumes that:

Habitat patches are of equal quality
Each occupied patch had the same sub population size
Each sub pop supplies the same number of dispersers to other patches

So species may be preserved by:
Protecting large fragments of habitat that reduce extinction risk
Or
Ensuring that individuals can disperse to and from patches

125
Q

Patch size and isolation

A

Habitat patches are rarely equal in quality

Some patches are larger or contain a higher density of resources

Small patches are likely to experience higher rates of extinction and less likely to be occupied than large patches

Dispersal success is inversely related to the distance of dispersal, so more distant patches will have a lower probability of being occupied than closer patches

Unoccupied patches that are close to occupied patches are more likely to be colonised and reduced

Rescue effect > when dispersers supplement a declining sub population and thereby prevent it from going extinct

126
Q

Successful use of metapopulation theory

A

Black footed ferret > numbers reduced by: habitat loss, poisons, disease

Thought extinct in 1979

Biologists conducted several reintroductions in locations throughout western North America

iPad

127
Q

Competition

A

Occurs when individuals experience limited resources

Decrease in a population density causes an increase in growth rate of population

128
Q

Leibigs law of the minimum

A

Not all resources limit consumer populations

The law states that a population increases until the supply of the most limiting resource prevents it from increasing further

Example > silica is a limiting resource for diatoms

Competition for a single limiting resource > the species that persists is the one that can drive down the abundance of that resource to the lowest levels

Leibig law assumes each resource has an independent effect on population growth so if you add more of another resource it will NOT improve the growth

129
Q

Interaction among species

A

An increase in one resource can have a much larger effect on a population when there is also an increase in a second resource

130
Q

Competitive exclusion principle

A

Two species cannot coexist indefinitely when they are both limited by the same resource

One species survives better when resources are scarce

131
Q

Competition > related species

A

Darwin suggested that competition is most intense between related species because they have similar traits and consume similar resources

Related species that compete strongly - differences in habitat use should be favoured

132
Q

Competition - non related species

A

Competition can also be intense among distantly related species that consume a common resource

133
Q

Different types of direct and indirect competition

A

Indirect - through a shared resource

Apparent - two species have a negative effect through an enemy, including a predator, parasite or herbivore

134
Q

Abiotic conditions

A

The ability to compete may well be overwhelmed by the ability to persist in harsh abiotic environments

135
Q

Disturbances

A

Competitive interventions can also be altered by disturbances or lack of

136
Q

Predation and herbivory

A

There are often trade offs between competitive ability and resistance to predators or herbivores

Predators can reverse the outcome of competition

Herbivores can also alter the outcome of competition

137
Q

Predators and herbivores can limit the abundance of species

A

All organisms face attack by natural enemies - critical in communities as they lower the pop size

This can reduce the importance of competition in some natural populations

In stable population cycles, both species can coexist

Herbivores - effects can be seen by fencing areas ore removing herbivores to prevent grazing

138
Q

Population cycles - pop of consumers and consumed populations fluctuate in retake cycles

A

The synchrony of population of population cycles between consumers and the populations they consume suggests that these oscillations are the result of interactions between them

139
Q

Predator prey cycles

A

Stable predator prey population cycles can be achieved when the environment is complex so that predators cannot easily find prey

Lotka volterra model - predator prey interactions incorporates oscillations in predator / prey and shows predator numbers lagging prey
BUT model does not incorporate time delays, density dependence or realistic foraging behaviour of most predators

Functional response: the relationship between the density of prey and an individuals predators rate of food consumption

Prey density increases then a predator can consume a higher proportion of those prey

Predators can regulate the growth of prey population

140
Q

Functional responses

A

Type 1: As prey density increases, predators consume a constant proportion of prey until satiation

Type 2: prey density increases and predators consumption of prey slows and plateaus.
Often happens because predators must spend more time handling more prey

Type 3: predator has low, rapid and slowing prey consumption

141
Q

Low consumption at low prey densities may occur for 3 reasons

A
  1. Refugees for prey to hide
  2. Predators may have less practice at locating and catching prey but develop a search image at higher prey densities
  3. Predators may exhibit prey switching by changing their diet preferences to the more abundant prey
142
Q

Herbivore population dynamics

A

Two types:

Interactive systems - herbivores affect plant populations traits

Non interactive - no relationship between herbivore densities and plant pop dynamics
One way: herbivores are affected, plants are not

143
Q

Evolutionary consequences

A

All organisms can defend themselves against attack

Can predators select for prey defence and prey for increased predator success?

144
Q

Predator hunting strategies

A

Active hunting - spend most of their time moving around looking for prey

Ambush - lie in wait for prey to pass

Hunting can be thought of as a series of events including:
Detecting, pursuing, catching, handling, consuming prey

145
Q

Prey defences

A

Behaviour - call, move away

Crypsis

Aposematism and chemical

Mimicry

Physical - tough leaves, spines, hairs, scales

146
Q

Communities can have distinct or gradual boundaries

A

Community > an assemblage of species living together in an area

Community zonation > species composition changes across a landscape, with changes in environmental conditions

Difference in: ranges for various environmental conditions and ability to compete with other species

147
Q

Communities are often categorised by

A

Dominant organisms or physical conditions that affect the distribution of species

148
Q

Ecotones

A

A boundary created by sharp changes in environmental conditions, over a relatively short distance and accompanied by a major change in the composition of species

Ecotones support a larger number of species from adjoining habitats, species specifically adapted to the Ecotone

149
Q

Biodiversity of a community

A

Diversity = species richness (number of species) + relative abundance (proportion of individuals of each species)

Log normal distribution > a normal, bell shaped, logarithmic scale on x axis

150
Q

Patterns of species abundance

A

Rank abundance curves > plots the relative abundance of each species in a community in rank order > from the most abundant to the least abundant

Species evenness > comparison of the relative abundance of each species in a community > if EVEN, all species = same abundance.

151
Q

Calculating biodiversity

A

Shannon’s index

Both richness and evenness of each community

Weighted to richness

Higher value = more diversity

152
Q

Simpsons diversity index

A

Both richness and evenness of each community

Gives more weight to dominant species eg. Abundance

Rare species will not affect index

Can use counts or percentage of cover

153
Q

Simspons similarity index

A

Compares richness and abundance between 2 communities

Gives more weight to dominant species ie. Abundance

154
Q

Effect of habitat diversity

A

Communities with higher diversity of habitats should offer more potential niches (eg. Places to feed and breed) and a higher diversity of species

155
Q

Keystone species

A

A species that substantially affects the structure of communities

Species might not be numerous

Removal of keystone species can cause a community to collapse

Ecosystem engineers > keystone species that affect communities by influencing the structure of a habitat

156
Q

Intermediate disturbance hypothesis

A

More species are present in a community that experience occasional disturbances compared to communities with frequent or rare disturbances

157
Q

Food web

A

A complex and realistic representation

Arrows in a food web indicate consumption and the movement of energy and nutrients

158
Q

Direct vs indirect effects

A

Direct > interaction between 2 species that does not involve other species

Indirect > intervention between 2 species that involves 1+ intermediate species, can occur between communities

Trophic cascade > indirect effects in a community that are initiated by a predator

159
Q

Top down and bottom up effects

A

Abundances of trophic groups are determined

Bottom up control > by the amount of energy available from producers

Top down control > by the existence f predators at the top of the food web

160
Q

How communities respond to disturbances

A

Community stability > ability of a community to maintain a particular structure

Community resilience > amount a community changes when acted upon by a disturbance eg. By addition or removal of a species

Community resilience > time taken for a community to return to its original state

161
Q

Alternative stable state

A

When a community is disturbed so much that species composition and relative abundance change AND the new community structure is resistant to further change

Switching to alternative stable states typically requires a large disturbance eg. Removing a keystone species

162
Q

Succession

A

Process by which the species composition of a community changes over time

Seral stage > each stage of community change during succession

163
Q

Pioneer species

A

The earliest species to arrive at a site

Typically able to disperse long distances

Arrive quickly at disturbed sites

Often ruderals

164
Q

Climax community

A

The final seral stage in the process of succession

Generally composed of organisms that dominate in a given biome

Often competitors

165
Q

Observing succession

A

Direct observation of changes over time is the clearest way to record succession in a community

Indirect > examining pollen preserved in layers of lake and and pond sediments and chronosequence - a sequence of communities that exist over time at a given location

166
Q

Primary succession

A

The development of communities in habitats that are initially devoid of plants and organic soil

Colonised by species - do not need soil, can live on rock surfaces

167
Q

Secondary succession

A

The development of communities in disturbed habitats that contain no plants but still contain organic soil eg. Ploughed field, forests uprooted by a hurricane

168
Q

Terrestrial succession

A

The sequence of seral stages that a site passes on its way to a climax community can differ depending on initial conditions

Chronosequence assumes sites pass through similar seral stages

169
Q

Animal succession

A

Changes in the plant community can change the habitats that are available to animals, which causes changes in the animal community

170
Q

Succession of intertidal communities

A

Succession in intertidal communities can occur rapidly after a disturbance due to the short generation time of dominant species

171
Q

Traits of species through succession

A

Early and Kate succession species have differing trade offs:

Dispersal, growth, reproduction, competitive ability

172
Q

Transient climax community

A

A climax community that is NOT persistent, occurs when a site is frequently disturbed so a climx community cannot persist

173
Q

Gaps in a climax community

A

Small scale disturbances in an area with a climax community can allow growth of species that are not considered climax species

174
Q

Extreme conditions

A

Fire maintained climax community > a successional stage that persists as the final seral stage due to periodic fires

Grazer maintained climax community > when a successional stage persists as the final seral stage due to intense grazing

Animal And Plant Ecology (1 decks)

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