The impact of deforestation on a tropical rainforest biome

There are three ways by which deforestation affects the tropical rainforest biome.

1. Habitat Destruction

Straightforward as it seems, deforestation fundamentally removes the habitat in which many organisms thrive on. As rainforest land is converted to ranches, agricultural land and urban areas for human use, forest organisms lose their habitat. Habitat destruction may only affect local population numbers in the short term. Yet species which are endemic, the ones that have specialized and limited habitats, this change can be extremely detrimental.

2. Forest Fragmentation

Fragmentation, or simply the loss of land area, seriously thwarts the reproduction of plant and animal populations. Since many tropical trees are pollinated by animals, the maintenance of adequate pollinator population is a must for helathy reproduction of trees. When a large forest becomes fragmented, many species of trees become isolated as their pollinators cannot cross the unforested areas. The trees in the fragmented areas will consequently lose genetic variability.

3. The 'Edge' Effect

Deforestation generates many “edges” in areas that previously used to be deep forests. As these areas become edges of the forest, they undergo significant environmental changes: they become lighter, warmer and windier than the forest interior. These changes in microclimate alter plant reproduction, animal distribution, the biological structure and many other features of the forest. The drier and warmer conditions also make the edges more prone to forest fires. Without further stress, the forest may regenerate.

Source: http://www.rainforestconservation.org/rainforest-primer/2-biodiversity/g-recent-losses-in-biodiversity/5-causes-of-recent-declines-in-biodiversity/

An itinerary to a tropical rainforest

(Image Source: http://www.blueplanetbiomes.org/rainforest.htm)
Long story short, I stand here in the vast tropical rainforest near the Amazon River basin, perhaps the very root of the Earth's ecosystem. It is ridiculously humid here. Even though I was fully aware that the Amazon rainforests typically belong to a tropical wet climate group that has an average humidity between 77 and 88% and precipitation above 100 inches a year, such humidity in mid April simply doesn't make any sense. Thank god that there are seasons of less rain between June and October depending on the region. Unlike what many people think, tropical rainforests do have dry seasons. Check out the graph below if you still can't believe me.

 (Source: http://www.unique-southamerica-travel-experience.com/amazon-rainforest-climate.html)



Now I feel I should stop complaining and talk about the environment here. Grabbing my attention the most amid this true wonder of nature are the trees.

(Source: footage.shutterstock.com)

So many trees, all having distinct features--I have never seen such an amazing diversity in my life. Scientists say that about 100 to 300 species of trees can be found in 1 hectare area in Amazon. These trees are not just eye pleasing but extremely beneficial to mankind. Can you believe that approximately one-fourth of all human medicines are from these rainforest plants?
Also very interesting are the examples of natural selection exhibited by these trees. Unlike the trees we see in temperate climate zones, I realized that these trees have thin, smooth bark.

(Source: footage.shutterstock.com)

Trees in tropical rainforests like Amazon have been free from harsh climates, meaning that they did not necessarily have to protect themselves from intense cold and aridity by developing strong barks. Rather posing practical threats to these trees were epiphytes and parasites that often attach themselves to the tree trunk and suck out the nutrients. Soft, thin barks have appeared as a consequence of such environmental factors, increasing the tree's chance of survival by protecting them from harm.

 

 

(Source: apexplanet.blogspot.com,  footage.shutterstock.com)

Just as intriguing as the trees were, the diverse plants of the Amazon rainforest also seem to bear evidence of adaptation. We see in the first picture how the leaves are curved towards the below. Such unique shape has been helpful in shedding off the heavy rain as quickly as possible so that the branches don't get overly weighed down. Shown in the second picture are enormous leaves that cannot be found in ordinary environments. Tropical rainforests lack sunlight due to their thick tree canopies. Larger the leaf, the more sunlight it will absorb. Simple as that.

 

(Source: http://cougarbiology.pbworks.com/w/page/9016280/Tropical%20Rainforest%20Group%20C)

 

I have never seen such strange animals in my life here. Animals that can be found here are clearly distinguished by their bright colors and showy patterns, which may also be interpreted in an evolutionary perspective. The prime advantage of having a colorful appearance is that an organism can attract mates better. Especially in a dim, shady environment like a tropical rainforest where visibility is not very high, the importance of maintaining such bright colors must have been immense for mating and reproducing. The bright colors also contribute to an organism's survival by giving a warning to its predators, indicating that the game is highly toxic.

Insects and bacteria are organisms that play a crucial role in the ecosystem of the rainforest. The soil of Amazon is extremely shallow and innutritious. Long, chronic rain has washed away the nutrients from the soil for tens of thousands of years, causing the environment to have a short nutrient cycle. Insects and bacteria quickly decompose the organic garbage accumulated in the soil and subsequently allow the plants to absorb the released nutrients. The ecosystem would not be sustained without these decomposers.


The Producers - the trees, shrubs, bromeliads and other plants.
The Primary Consumers – the macaws, monkeys, agouti, tapir, butterflies, sloths, toucans.
The Secondary Consumers – the jaguar and boa constrictor.
The Scavengers –  the butterflies and  other insects.
The Decomposers or Detrivores – mushrooms, insects and microorganisms (bacteria).

(Source: http://www.exploringnature.org/db/detail.php?dbID=2&detID=1220)


bibliography:
"Introduction", http://www.hqlist.demon.nl/gvg/ctkoppen.htm (Nov 2000)
"Köppen Biomes", http://www.tesarta.com/www/resources/library/biomes.html (Dec 2000)
"Rainfall", http://encarta.msn.com/find/print.asp?&pg=8&ti=00531000&sc=29&pt=1 (Dec.2000)
"Temperature", http://encarta.msn.com/find/print.asp?&pg=8&ti=00531000&sc=29&pt=1 (Dec.2000)
Allaby, Michael, Biomes of the world volume 7 Oxford: Anndromedia Limited1999
Kellert, Stephen R. Macmillion Encyclopedia of the Environment. Simon and Schuster and Prentice Hall International. 1997
"Rainforest Climate", http://passporttoknowledge.com/rainforest/GEOsystem/Rainforests/climate.html (March 2001)
Stralhler, Arthur N. Strahler, Alan H. Elements of Physical Geography . John Wiley & Sons. 1997.

Pillbug lab--Animal behavior

1. Abstract

     Using pillbugs so as to observe animal behavior, a series of labs was conducted in a behavior chamber divided into two areas both covered with filter paper. My parter and I observed pillbug behavior for 7 minutes and 30 seconds for each lab, recording lab data (number of pill bugs in each area) every 30 seconds. The first lab showed that pillbugs strongly prefer a wet environment to a dry one, the second lab that pillbugs, albeit moderate, prefer an environment of high sugar content, and the third that pillbugs have fairly strong affinity to rocky terrains artificially created with beads.

 

2. Introduction

     Animal behavior is, to rephrase the definition written in the pre-lab handout distributed beforehand, an animal's response to external stimuli. The study of animal behavior consists of two different types of questions: proximate questions and ultimate questions. Proximate questions are focused on the ostensible mechanics of a particular behavior. An example of a proximate question regarding bird song would be ‘how often and long does the bird sing?’ or ‘what muscles enable the bird to sing?’ Ultimate questions, on the other hand, deal with more fundamental causes of a behavior mainly pertaining to the evolutionary reasons. One ultimate question regarding bird song is ‘how does the singing affect the bird’s chance of survival in the ecosystem?’ Fixed action pattern is an animal’s instinctive, genetically inherent behavioral response to what’s called a sign stimulus, an occurrence of a particular situation that stimulates an animal to show the response. Prominent examples of fixed action pattern include mate dancing of birds and aggression between male sticklebacks (Wikipedia, s.v. fixed action pattern). Imprinting refers to the process by which an animal acquires a certain reaction mechanism to a particular stimulus that soon becomes an instinct. For instance, a baby goose, between 13 to 16 hours after hatching (Wikipedia, s.v. imprinting), a period known as a ‘critical period’, would ‘imprint’ on its memory a particular subject (not necessarily an adult goose) as its lifelong guardian. Kinesis and taxis are two types of animal responses—kinesis is a random, undirected reaction to a stimulus, and taxis a specific one with well-guided directions. The pillbug experiment gives good sense of the two concepts. Taxis occurred when pillbug moved from one area to another in accordance with its preference of light, heat, moisture, sound or chemicals. Kinesis was exhibited when the pillbugs simply moved around the filter paper regardless of the stimulus. Classical conditioning is a type of learning in which the repeated memories of a certain stimulus trigger an involuntary reaction to another stimulus. After experiencing loud thunderstorms at least once in our lifetimes, we automatically close our ears when we see a lightening from the sky due to classical conditioning. Operant conditioning refers to a learning of a behavior aimed for practical benefit or reward. When a dog, knowing that he will be rewarded with a treat afterwards, obeys his master’s order to sit down, a perfect example of operant conditioning has been exhibited.


3. Hypotheses

         Independent variable: water (wetness of the filter paper), honey (sugar content of filter paper), beads (rockiness of the terrain)

         Dependent variable: Number of pillbugs in each chamber

A.   Moisture Lab

If a wet environment is created, the pillbugs would exhibit taxis by moving there instead of staying in a dry one.

B.    Honey Lab

If we drench one chamber with honey, the pillbugs would be attracted to it due to its general preference of sugar, also exhibiting taxis.

C.    Terrain Lab

       

If a rocky terrain is formed, the pillbugs, exhibiting kinesis until it reaches there, would eventually show the tendency to prefer a rockier environment.

 

4. Materials

- 10 pill bugs

- 3 behavior chambers

-approximately 10mL of water

-app. 10ml of honey

-around 50 beads

-Brushes

-6 pieces of filter paper

 

 

5. Procedure

 

A.   Place 10 pillbugs in a behavior chamber whose two rooms are covered with filter papers. One should always remain dry as a control.  

B.    Record the number of pillbugs every 30 seconds in each room, carefully observing their behaviors.

C.    After at least 7 minutes, put the pillbugs back into the beaker using brushes. Prepare for the next experiment, changing the independent variable.

 

6. Results

 

A. Moisture lab:

 

Time (minutes)	# in dry chamber	# in wet chamber
0	2	8
0.5	2	8
1	2	8
1.5	2	8
2	1	9
2.5	1	9
3	0	10
3.5	0	10
4	0	10
4.5	0	10
5	0	10
5.5	0	10
6	0	10
6.5	0	10
7	0	10

 

The initial hypothesis was true. Pillbugs definitely preferred a wet environment to a dry one.

 

B. Honey Lab

 

Time (minutes)	# in dry chamber	# in honey chamber
0	2	8
0.5	2	8
1	2	8
1.5	2	8
2	3	7
2.5	3	7
3	3	7
3.5	2	8
4	3	7
4.5	2	8
5	1	9
5.5	3	7
6	4	6
6.5	4	6
7	3	7

Belying our initial hypothesis that pillbugs would show strong affinity to honey, the pillbugs were rather evenly spread in both chambers, albeit exhibiting a moderate preference of honey.

C. Terrain Lab

Time (minutes)	# in dry chamber	# in bead chamber
0	0	10
0.5	1	9
1	3	7
1.5	5	5
2	6	4
2.5	5	5
3	7	3
3.5	6	4
4	7	3
4.5	9	1
5	10	0
5.5	9	1
6	10	0
6.5	8	2
7	9	1

 

The preference of an uneven terrain was very obvious at first, but the pillbugs soon started to freely move around, perfectly exhibiting kinesis. However, since their behavioral tendency to gather around the beads was very dramatic, I would still call the initial hypothesis valid.

7. Conclusion

Apart from superficial observations, the lab suggests a significant ultimate question regarding adaptive traits often maintained and evolved through natural selection. The behavioral tendencies pillbugs demonstrated were in many cases related to adaptive traits acquired so as to increase their chances of survival in nature. Pillbugs, over time, have evolved/adapted to live under dark, damp objects such as trees or organic garbage to avoid their predators. This accounts for their preference of wet filter paper. Sugar can possibly be a good source of nutrient for the pillbugs to generate ATP. Pursuit of sugar must have been beneficial to their survival. Likewise, pillbugs are fond of rocky terrains for they are capable of inhabiting under rocks, a desirable trait that prevents them from being noticed by predators.