The document discusses key concepts relating to species, populations, and ecological niches. It defines a species and explains factors that influence populations like biotic and abiotic interactions. Population growth is described using S-curve and J-curve models, showing exponential then limited growth as carrying capacity is approached. Ecological niches are influenced by both fundamental and realized factors, and examples of population interactions like competition and predation are provided.

1. 2.1. Species and populations
Miltiadis Kitsos
Platon school IB diploma
https://cdn.thinglink.me/api/image/905647632154624002/1240/10/scaletowidth

2. 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.

3. 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.

4. 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.

5. 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

6. 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

7. 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:

8. 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.

9. 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

10. Species scientific name (italics)
Species common name Photo
IUCN status
Habitat

11. 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/P13
70796.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.

12. Ecological niche
A niche may range from a unidimensional space to a multidimensional space.
Begon et al. Ecology: From individuals to ecosystems

13. 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

14. 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
live
Where a
species actually
exists

15. Abiotic factors
Abiotic factors are the non-living parameters of the environment
Optimal range
Tolerance range
Speciesabsent
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/r4wylsnp9rs
http://image.wikifoundry.com/image/3/z8AkjyDVgKrRi-pX8MmHWQ271398/GW465H314

16. 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

17. Population interactions
Predation is controlled by a negative feedback mechanism
The predator population is responding
with a lag to prey population changes.

18. 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

19. Population interactions
Parasitism – Living on the expense of another organism
https://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Cym
othoa_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_Tetragn
atha_montana_%28RMNH.ARA.14127%29_parasitized_by_Acrodactyl
a_quadrisculpta_larva_%28RMNH.INS.593867%29_-_BDJ.1.e992.jpg
A parasitoid wasp (Acrodactyla
quadrisculpta) on a spider
https://youtu.be/vMG-LWyNcAs

20. 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

21. 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

22. 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

23. 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

24. 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

25. 1
2
3
4
Population growth
Population 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

26. Population growth
Population 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.

27. Population growth
Case 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

28. Population growth
Some 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

29. Population growth
Some 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

30. 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.