DP Biology Topic 4.1 Species, Communities, & Ecosystems

1. 4.1 Species, Communities & Ecosystems
IB Biology
R. Price
v. 1 2015

2. Allott, 201

3. #1 Species are groups of organisms that can potentially interbreed to produce fertile offspring
#2 Members of a species may be reproductively isolated in separate populations
Discussion: Galapagos tortoises
The tortoises that live on the Galapagos islands are the
largest in the world. They have sometimes been grouped
together into one species, Chelinoidis nigra, but more
recently have been split into separate species.
Discuss whether each of these observations indicates that
population on the various islands are separate species:
• The Galapagos tortoises are poor swimmers and
cannot travel from one island to another so they do not
naturally interbreed.
• Tortoises from different islands have recognizable
differences in their characters, including shell size and
shape.
• Tortoises from different islands have been mated in
zoos and hybrid offspring have been produced but they
have lower fertility and higher mortality than the
offspring of tortoises from the same island.
Allott, 203

4. Understanding #3-6
#3: Species have either an autotrophic or heterotrophic method of nutrition (a
few species have both methods).
• Autotrophic = self-feeding, make carbon compounds from carbon dioxide
• Heterotrophic = eat other organisms (i.e. plants, animals)
#4: Consumers are heterotrophs that feed on living organisms by ingestion.
#5: Detrivores are heterotrophs that obtain organic nutrients from detritus by
internal digestion.
• Eat dead leaves, feather, hairs, feces, etc.
#6: Saprotrophs are heterotrophs that obtain organic nutrients from dead
organic matter by external digestion.
• Often referred to as “decomposers”
• Bacteria & fungi are commonly saprotrophs

5. Allott, 204

6. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Common Blue Butterfly (Polyommatus Icarus) Diet of the adult includes
wildflower nectar and excrement.

7. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Squirrels are members of the family Scuiridea. Squirrels can not
digest cellulose, so they must eat foods rich in protein, carbohydrates,
and fats. Some typical foods include: nuts, seeds, fungi, and insects.

8. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Euglena gracilis has been used extensively as a
model organism in the laboratory. They have
photosynthesizing chloroplasts and they can also
ingest food particles by phagocytosis.

9. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Earthworms are a segmented worm found in the phylum Annelida. Various
species of worms are used in vermiculture, the practice of feeding organic
waste to earthworms to decompose food waste. The worm “castings” are a
nutrient rich natural fertilizer that is easy for plants to use.

10. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Pitcher plants are found in soils that are too low in nitrogen or phosphorus or are
too acidic for most other plants to grow. They have chloroplasts and use
photosynthesis to produce ATP. To obtain other vital nutrients, such as nitrogen,
they lure and drown insects. Either beneficial bacteria or their own enzymes
break down the insects and the pitcher plants absorbs the needed nutrients.

11. Identifying modes
of nutrition
A. Autotroph
Heterotroph
B. Consumer
C. Detrivore
D. Saprotroph
Molds are microbes and can cause the biodegradation of natural materials. They
secrete hydrolytic enzymes. These enzymes degrade starch, cellulose and
lignin into simpler substances which can be absorbed by the mold.

12. #11 Ecosystems have the potential to be sustainable over long periods of time
Skill: Setting up sealed mesocosms to try to establish sustainability (Practical 5)

13. Mesocosm Project (Practical 5)
 Timeline: One academic quarter
 Research: mesocosm, bottle garden, terrarium.
 Mesocosm type: Sealed, aquatic and/or terrestrial
 Design: What materials are available? What do you wish to observe?
 Ethics: IB Animal Experimentation Policy
 Communication: Website or blog. Must be updated at least once per week.
 Evaluate: During the last week of each calendar month, evaluate your progress. Suggest refinements.

14. #7: A community is formed by populations of different species living together and interacting with each other
#8 A community forms an ecosystem by its interactions with the abiotic environment
Skills: Testing for associeation between two species using the chi-squared test with data obtained by quadrat sampling
Skills: Recognizing & interpreting statistical significance.
Allott,
209

15. Allott, 210

16. Allott, 207

17. Allott, 208

19. Allott, 209

20. Sources
Content
Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014
ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge:
Cambridge UP, 2014. Print.
Images
Unless otherwise noted, images are obtained from Pixabay
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