Topic 3 - Ecology

Question 1

Define semelpartiy and iteroparity

Answer 1

• Semelparous: individuals breed once in their life. They have one reproductive event and then die
• Iteroparous: individuals can breed multiple times in their life.

Question 2

Define annual and perennial reproduction strategies

Answer 2

• Annuals complete their life cycle in one year or less
• Perennials have a repeated breeding season at predictable times each year

Question 3

Define fecundity

Answer 3

• An organism’s reproductive capacity (no. offspring it’s capable of producing)

Question 4

Define parental investment

Answer 4

• The energetic investment into each offspring

Question 5

Describe early reproduction strategies:

Answer 5

• Short-lived, smaller in body size
• Geared towards early energy going toward reproduction instead of growth
• Reduces risk of not reproducing at all

Question 6

Describe late reproduction strategy

Answer 6

• Long-lived, larger in body size
• Geared toward putting energy into growth to a larger size where mortality rates are lower, than later in life insetting energy in reproduction
• Higher risk of not reproducing at all or to max capacity if death occurs early.

Question 7

Explain the features of r and k selected species

Answer 7

• K selection is the selection for traits that are advantageous in high density populations
• R selected species is the selection for traits that maximise reproductive success in uncrowded or low-density populations

Question 8

Define population ecology

Answer 8

• Pop ecology is the study of populations in relation to the environment and resources
• Population: A group of individuals of the same species living in the same location with the individuals relying on the same resources, influenced by similar environmental conditions and interacting with each other.

Question 9

Explain the properties of an ecological population using examples

Answer 9

• Boundaries: natural, arbitrary, matches the purpose of the study and the organism
• Size: how many individuals in a population and what changes the number of individuals (births, deaths, immigration, emigration)
• Distribution: the extent to which individuals are spaced in a population
• Structure: the characteristics of the individuals that make up the population (sex ratio, age structure)

Question 10

Explain an application of population ecology

Answer 10

• Species management – endangerment
• Pest control
• Disease dynamics

Question 11

Understand how to estimate population size

Answer 11

• Full census: counting every individual
• Sampling: estimating
• Imperfect detection: N (abundance) = n (number seen) / P (probability of detection)

Question 12

Describe the limitations and assumptions for different methods

Answer 12

• Mark -recapture
• Capture, mark, release, recapture
• Assumptions: marks are durable for length of study, marks don’t decrease survival, probability of recapture remains consistent, closed population (no births, deaths, immigration, emigration)

Question 13

Define demography in your own words

Answer 13

• The study of the birth and death rates of populations and how they change over time

Question 14

Identify important aspects of a life history table

Answer 14

• Life history is all the events involved in an organism’s survival and reproduction
• Age class (years)
• Number of survivors
• Number of young per year
• Fecundity per surviving individual

Question 15

Explain the three categories of survivorship curves

Answer 15

• Type 1: most individuals die later in life (k strategist)
• Type 2: log scale, negative linear relationship between number of survivors and years (uniform rate of decline)
• Type 3: number of survivors rapidly drops and is low in numbers as time progresses (exponential decay) (huge decline in young) (r strategist)

Question 16

Describe the features of a population growth model.

Answer 16

• Mathematical models that estimate change in population size over time
• X axis is time
• Y axis is population size

Question 17

Explain an exponential growth model

Answer 17

• Populations growing under ideal conditions: unlimited resources and no limiting growth
• Growth rate is constant
• Accelerating growth as individuals increase
• N(t)= N0*ert
• Nt = population size at time t
• N0 is initial population size
• R is intrinsic growth (birth rate minus death rate)

Question 18

Explain a logistic growth model

Answer 18

• Starts off exponentially and then growth slows, carrying capacity is reached, and resources limit population
• More realistic

Question 19

Describe density-independent population growth

Answer 19

• Often abiotic factors
• Change in the population size regardless of the population density
• Sever events: heat waves, storms, pollution

Question 20

Describe density-dependent population growth

Answer 20

• Change in population growth depending on the number of individuals in the population
• Competition for resources
• Predations: attracted to dense population of prey causing large deaths
• Disease: spreads easily in dense populations

Question 21

Explain the effects of environmental and demographic stochasticity of population size

Answer 21

• Environmental stochasticity: unpredictable fluctuations in environmental conditions that influence population dynamics by changes in birth and death rates
• Demographic stochasticity: change in birth and deaths of individuals caused by chance

Question 22

Explain the role of source of sink populations in conserving a species from extinction

Answer 22

• Source population: support local population growth and can be net exporters of individuals (emigration) to other patches
• Sink population: mortality exceeds births and populations are reliant on immigration to persist
• Metapopulations are groups of isolated populations linked together by dispersal and have patchy distributions. Metapopulations allow individuals to disperse between source (donor) and sink (recipient) populations to reduce extinction probability.

Question 23

Describe the types of strategies predators use to obtain food

Answer 23

• Active pursuit
• Stealthy ambusher

Question 24

Describe the types of strategies prey use to avoid being captured

Answer 24

• Avoiding detection: camouflage
• Chemical defences: smaller animals
• Warning signals: common in marine systems, used with chemical defences
• Mimicry systems: the mimic closely resembles a dangerous or toxic species
• Behavioural mechanisms: group flocking, alarm vocalisation

Question 25

Compare and contrast the concepts of fundamental niche and realized niche

Answer 25

• Niche: the physical and biological conditions required for growth, reproduction, and survival
• Fundamental niche: a species’ physiological capabilities in ideal conditions
• Realised niche: a species’ physiological capabilities, constrained by interactions with other species such as competition and predation

Question 26

Distinguish between interference competition and exploitation competitions

Answer 26

• Interference competition: occurs when one species directly interferes with or excludes another species’ access to a limiting resource
• Exploitation competition: occurs when a limiting resource is available to all competitors, but the outcome of the interaction depends on the relative efficiency with which each species uses the resource

Question 27

Describe competitive coexistence using a biological example

Answer 27

• Competitive coexistence: the ability of multiple species to live together in the same ecological niche despite competition for the same resources

Question 28

Define dispersal using an example

Answer 28

• Dispersal is the movement from one breeding location to another
• Natal: from birthplace to first breeding place
• Breeding: change of place of breeding

Question 29

Describe the different types of dispersal modes used by animals and plants

Answer 29

• Animals: active (flying, walking, swimming) and passive (currents, floods, attached to animals, vehicles)
• Plants: gravity, wind, water, animals (on or in guts), vehicles/machinery

Question 30

Explain the difference between dispersal and migration

Answer 30

• Dispersal: spreading of individuals away from others and occurs early in life or as adult
• Migration: large-scale movement of members of a species to a different environment

Question 31

Describe types of symbiosis and whether they typically help, harm, or have no effect on the organisms involved.

Answer 31

• Commensalism: one species benefits while the other is unharmed
• Mutualism: both species benefits
• Parasitism: one species benefits while the other is harmed

Question 32

Explain the unique traits and life cycles of parasites, given their habitat is a living host

Answer 32

• Traits:
  o Smaller than host
  o Live on or in the host for extended periods of time
  o Usually don’t kill hosts (but can)
  o Hosts can recover
  o The hosts of parasites can grow, mount defences against parasites, evolve, and move
• Monoxenic: one host
• Heteroxenic: multiple hosts

Question 33

Describe the abundance, diversity and types of parasites in nature

Answer 33

• Protozoans: single-celled, animals, fungi, plants
• Microparasites: intra-cellular, multiple directly within hosts, numerous, viruses/bacteria
• Macro-parasites: grow on or in hosts but don’t multiple with host, produce infectious stages which they release into the environment to find new host,
• ½ of arthropods are parasitic
• The biomass of parasites (total weight of all individuals in a group) can outweigh a conspicuous animal

Question 34

Explain and give examples of kleptoparasitism

Answer 34

• Parasitism by theft – one animal deliberately taking food from another
• Seabirds: steal fish from each other and chase/harass others until they drop their food

Question 35

Explain the characteristics of mutualistic and commensal relationships with examples

Answer 35

• Pollinations and seed dispersal: mutualistic – reward: pollen and fertilisation for the plant
• Corals are endosymbionts with zooxanthellae – zooxanthellae consume wastes and corals take products of photosynthesis
• Commensalism: epiphytes grow on other plants without disturbing them

Question 36

Explain the concept of animals and plants that are considered pests or weeds

Answer 36

• Organisms with populations that are unnatural or too large meaning they come into conflicts with other interests
• Damaging to agriculture, valued species, environment, and biodiversity

Question 37

Describe the different types of biological control and the considerations needed to make them effective

Answer 37

• Classical biological control: the deliberate importation and release of new species – aims to import natural enemies that are missing
• Augmentative biological control: repeated rearing and release of natural enemies – locally available rather than imported – natural enemies are reared and released into crops
  o Inoculative augmentation (long term): control by released enemies and their progeny
  o Inundative augmentation (short term): control exclusively by the released enemies
• Conservation biological control: promoting/protecting existing natural enemies – modification of the environment or existing practices to protect and enhance natural enemies to reduce effects of pests

Question 38

Describe the differences between epidemic and endemic diseases, how they affect populations, and how they can be controlled

Answer 38

• Epidemic: increase rapidly in smaller geographic areas
• Endemic: disease is constantly present in a population subset