2.1. Species and populations

Miltiadis Kitsos

Platon school IB diploma

https://cdn.thinglink.me/api/image/905647632154624002/1240/10/scaletowidth

Significant ideas

• A species interacts with its abiotic and biotic environments, and its niche is described by these

interactions.

• Populations change and respond to interactions with the environment. Any system has a carrying

capacity for a given species.

Knowledge and understanding

• A species is a group of organisms that share common characteristics and that interbreed to produce

fertile offspring.

• A habitat is the environment in which a species normally lives.

• A niche describes the particular set of abiotic and biotic conditions and resources to which an

organism or population responds.

Knowledge and understanding

• The fundamental niche describes the full range of conditions and resources in which a species could

survive and reproduce.

• The realized niche describes the actual conditions and resources in which a species exists due to

biotic interactions.

• The non-living, physical factors that influence the organisms and ecosystem—such as temperature,

sunlight, pH, salinity, and precipitation—are termed abiotic factors.

• The interactions between the organisms—such as predation, herbivory, parasitism, mutualism,

disease, and competition—are termed biotic factors.

•

• Interactions should be understood in terms of the influences each species has on the population

dynamics of others, and upon the carrying capacity of the others’ environment.

Knowledge and understanding

• A population is a group of organisms of the same species living in the same area at the same time,

and which are capable of interbreeding.

• S and J population curves describe a generalized response of populations to a particular set of

conditions (abiotic and biotic factors).

• Limiting factors will slow population growth as it approaches the carrying capacity of the system.

Applications and skills

• Interpret graphical representations or models of factors that affect an organism’s niche. Examples

include predator–prey relationships, competition, and organism abundance over time.

• Explain population growth curves in terms of numbers and rates.

The species concept

A species is a group of organisms sharing common characteristics that can interbreed and produce o

spring that can also interbreed and produce young.

In some cases two species [e.g., the horse

(Equus caballus) and the donkey (Equus

asinus)] can produce offspring which however,

can not produce fertile offspring (e.g. mule)

Equus caballus Equus asinus

When species are discovered they are given scientific names using the binomial system.

The binomial system

http://upload.wikimedia.org/wikipedia/commons/8/8c/Chaceon_affinis.j

pg

Chaceon affinis (A. Milne-Edwards & Bouvier, 1894)

Latin (written in italics)

Genus name (capitalized)

Species name (lower-case)

authority (scientist(s) that gave first full

description)

Find out more about this species, http://www.marinespecies.org/aphia.php?p=taxdetails&id=107369

The species concept

• can not identify whether geographically isolated

populations belong to the same species

• Can not classify species in extinct populations

• Does not account for asexually reproducing

organisms.

• Does not clearly define species when barriers to

reproduction are incomplete

https://evolution.berkeley.edu/evolibrary/images/interviews/ranges_map.jpg

This definition of the species has certain limitations:

The habitat concept

• A habitat is the environment in which a species normally lives.

The preferred habitat of the polar bear (Ursus

maritimus) is the annual ice near the coastlines of

continents and islands, where there are large numbers of

ringed seals (Phoca hispida), on which these bears feed.

The ring-tailed lemur (Lemur catta) is commonly found

in the dry forests and bush of southern and

southwestern Madagascar. Also found in spiny and,

lowland gallery forest, dry scrub, and even rock

canyons.

All images and text from arkive.com and IUCN.

Your turn now..

• Visit arkive.com and find two species of your liking. Then using the information from the site try to

complete the information in the next slide. Then, do a short presentation in class.

• All slides from this activity will be available on my site for future reference.

http://www.arkive.org/media/25/25C64A93-B0CD-4EF9-B93A-CED5B6C8D8D9/Presentation.Large/Six-month-old-snow-leopard-in-snow-controlled-situation.jpg

Species scientific name (italics)

Species common name Photo

IUCN status

Habitat

Ecological niche

An ecological niche is best described as where, when, and how an organism lives.

The niche is not only about the habitat of a species but how this species functions in its habitat. A niche is not a place

but an idea: a summary of the organism’s tolerances, variable ranges and requirements.

https://static.independent.co.uk/s3fs-public/thumbnails/image/2015/08/06/10/hippo-alamy.jpg

http://1.bp.blogspot.com/-xsfYPcdQZOU/VVch8Q0DshI/AAAAAAAAf4o/j__I85QaG94/s1600/P1370796.JPG

http://1.bp.blogspot.com/-xsfYPcdQZOU/VVch8Q0DshI/AAAAAAAAf4o/j__I85QaG94/s1600/P1370796.JPG

Use these photos to describe aspects of the hippopotamus's niche.

Ecological niche

A niche may range from a unidimensional space to a multidimensional space.

Begon et al. Ecology: From individuals to ecosystems

Ecological niche

Every species has its own unique niche which actually defines this species.

Outline the similarities and

differences in the

fundamental niches of

these two barnacle species.

http://www.hammiverse.com/lectures/53/images/1-1.jpg

Ecological niche

Fundamental vs realized niche

In most cases there is a difference between the niche a species can theoretically occupy (fundamental

niche) and the one it actually does (realized niche)

http://www.hammiverse.com/lectures/53/images/1-1.jpg

http://climatesmartnetwork.org/wp-content/uploads/2015/07/Figure1-Climate-Niches.jpg

Full potential of

where, when a

how a species may

liveWhere a

species actually

exists

Abiotic factors

Abiotic factors are the non-living parameters of the environment

Optimal range

Tolerance range

Specie

s a

bsent

Optimal and tolerance range refer to

a combination a factor although

there are cases where a single

factor may be the limiting one.

https://youtu.be/r4wylsnp9rshttp://image.wikifoundry.com/image/3/z8AkjyDVgKrRi-pX8MmHWQ271398/GW465H314

Population interactions

Predation – when a species hunts, kills and eats another species

https://youtu.be/8ma095zyzAM

https://biologydictionary.net/wp-content/uploads/2016/10/Cheetah-Hunting.jpg

https://visityellowstonenationalparkyall.weebly.com/uploads/1/9/1/2/19128651/7653699_orig.jpg

http://trttemperaterainforest.weebly.com/uploads/1/7/3/7/17371767/201265912.jpg?409

Population interactions

Predation is controlled by a negative feedback mechanism

The predator population is responding

with a lag to prey population changes.

Population interactions

Herbivory– when a species eats a plant species

http://trttemperaterainforest.weebly.com/uploads/1/7/3/7/17371767/201265912.jpg?409

http://alessandrabenton.com/wp-content/uploads/2012/05/A-Light-Dazzle1200x800.jpg

http://1.bp.blogspot.com/-Uy0oqq8p3Go/VDBp0IqsHCI/AAAAAAAAA9o/tF34mUVlLIA/s1600/50%2Bmonarchcaterpillar.jpg

https://youtu.be/oWOC8trquFo

Population interactions

Parasitism – Living on the expense of another organism

https://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Cymothoa_exigua_parassita_Lithognathus_mormyrus.JPG/1280px-Cymothoa_exigua_parassita_Lithognathus_mormyrus.JPG

A species of the genus

Lithognathus fish with the parasitic

isopod, Cymothoa exigua,

https://upload.wikimedia.org/wikipedia/commons/6/65/Live_Tetragnatha_montana_%28RMNH.ARA.14127%29_parasitized_by_Acrodactyla_quadrisculpta_larva_%28RMNH.INS.593867%29_-_BDJ.1.e992.jpg

A parasitoid wasp (Acrodactyla

quadrisculpta) on a spider

https://youtu.be/vMG-LWyNcAs

Population interactions Mutualism– where two species benefit from their symbiosis

http://www.scienceclarified.com/photos/symbiosis-real-life-applications-2942.jpg

https://68.media.tumblr.com/3f0fa3bf5a93bda5aabc96fa48d226e5/tumblr_olw95gCcpu1vmlgf6o6_540.jpg

https://lh4.googleusercontent.com/1-oOcCWuhTcGbWfN80RglrIqPyzaOld5hZSfkGmNz_3-T44m2CBWPhiUbmoxaoppkujHjrEsTrunqzJd2nSA6LINrkVvPwjuzLyn9smINRVjoMBzdDtQTLi77wCqXL2N=s1600 https://youtu.be/Qqa0OPbdvjw

Population interactions Competition – when resources are limited

https://media.buzzle.com/media/images-en/gallery/mammals/deers/1200-500492488-deer-fighting.jpg

http://www.wired.com/images_blogs/wiredscience/2011/09/hyenas-lions-gnu-660x495.jpg

http://www.prism.gatech.edu/~gh19/b1510x/f5501.jpg

https://youtu.be/AiTG6T9pTcM

Population interactions Competition – when resources are limited

http://www.prism.gatech.edu/~gh19/b1510x/f5501.jpg

Competition may be intraspecific that is among

the individuals of the same species or

interspecific that is, among different species (in

this case between Chthamalus and Balanus)

Begon et al. Ecology: From individuals to ecosystems

Population interactions Competition – when resources are limited

No species occupy the same niches. Niche

overlap will determine intensity of

competition.

These two species of Paramecium when

grown in the same culture they compete for

food and space and finally P. caudatum is

outcompeted.

http://slideplayer.com/9110552/27/images/11/When+cultured+in+isolation%2C+the+population+density+of+each+species+of+Paramecium+increases+rapidly+and+then+levels+off.jpg

Population growth

Population growth curves – The S curve

Low population density-

intensity of limiting factors

low

Exponential growth

Increased competition as the carrying

capacity is reached

1

2

3

4

Population growthPopulation growth curves – The S curve

Stage Name Notes

1 Lag phase Low population density

(number of individuals/unit

area) leading to low birth

rates.

2 Exponential

growth phase

There are environmental

conditions that allow the

exponential growth of the

population.

Limiting factors (e.g.,

predation) are not limiting

growth

3 Transitional

phase

Limiting factors (e.g,

competition) restrict

population growth

4 Stationary

phase

Population has reached its

carrying capacity. Carrying capacity: the maximum number

of individuals of a species that can be

supported in a given area

Population growthPopulation growth curves – The J curve

There are certain populations that would show a J-shaped curve instead of an S-

shaped. These species have usually an R-strategy, meaning:

• they tend to produce many offspring in a very short period of time

• they demonstrate little parental care.

However, these populations may demonstrate a very

sharp decrease of their abundance which is known

as a population crash or dieback.

These collapses often follow a long-term increase of

the population above the carrying capacity. This is

called overshoot.

overshoot

Carrying capacity

Exponential

growth

dieback

time

S and J population curves are models, and as models they describe a generalized response of populations to a particular set of conditions (abiotic and biotic factors).

In practice, the growth curve of each population looks like a combination of an S- and a J-curve.

Population growthCase study: The introduction, increase and crash of reindeer on St. Matthew island

St Matthew island is a small island in the Bering sea

near Alaska.

https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/St._Matthew_Island_Reindeer_Population.svg/512px-St._Matthew_Island_Reindeer_Population.svg.png

https://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Stmatthewisland.png/1920px-Stmatthewisland.png

Reindeer (Rangifer tarandus), introduced to St. Matthew

Island in 1944, increased from 29 animals at that time to

6,000 in the summer of 1963 and underwent a crash die-

off the following winter to less than 50 animals since the

carrying capacity of the island was over-reached.

http://www.weatherwise.org/sebin/i/z/Reindeer-Photo-6.gif

Population growthSome more information on population ecology

In the exponential growth phase:

• The limiting factors do not restrict the growth of population.

• Resources are in abundance• The environmental variables are favoring population

growth.

• Natality > mortality; immigration > emigration

Common limiting factors: for plants: light intensity, nutrients, water availability, and temperature for animals: food resources, mates, nesting sites, and water availability

Population growthSome more information on population ecology

In the stationary growth phase:

• The limiting factors are restricting the growth of population since the carrying capacity has been reached.

• The population demonstrates minor fluctuations around the carrying capacity.

• Resources are not in abundance, triggering competition.

Carrying capacity

References

Andrew, Davis, et al. Pearson Baccalaureate Environmental Systems And Societies For The Ib Diploma.

Rutherford, Jill. Environmental Systems and Societies. Oxford University Press, 2015.