Ecological Succession PDF

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Ecological Succession A pioneer species is the first species that inhabits a barren area and begins the process of ecological succession. **Ecological succession is the process through which an ecological community develops and changes over time. This process is often predictable, and it either occurs in a new habitat or after a disturbance (such as a forest fire or mass extinction). The types of species present in the community change throughout this process, and it can occur over decades to millions of years. Ecological succession comes in two different varieties: primary succession and secondary succession.

Primary succession happens after a large disturbance (like a volcanic eruption) or on a substrate that had not previously supported life (like a rocky terrain). It occurs on a substrate that completely lacks plant and animal life. The process begins with pioneer species (lichen, algae, and fungi are classic examples), in combination with abiotic factors such as water and sunlight. Once a thin layer of soil has formed, vascular plants, like grasses and shrubs, join (or replace) the pioneer species. Eventually, the community may be able to support larger plants, like trees. And, as the community changes, more and more animals become attracted to and join this community. Eventually, a climax community ****may be established. A climax community results when the ecological succession process has reached a steady state and there is a balance in the prevalence of each species. https://lh3.googleusercontent.com/2IrD_AabxA2o3O7vSDSl0Fgo22mRHCYzR5z0h06_y8FVdU 8bKko38Lbk1vJ8-JX1nzfV1tGJVb3SAWl9td75BJudDGP3HV84u7ay_BIGFvX5Nnvx3KnuAorrZ_ Zq3XSnO-L_45qf https://commons.wikimedia.org/wiki/File:AP_Biology_-_Primary_Succession_Drawing.svg

Secondary succession follows a similar pattern to primary succession. However, unlike primary succession, secondary succession follows a smaller disturbance, such as a flood or fire. Hence, the succession process happens on terrain that has already supported life. Since soil is already present, this process begins with the establishment of grasses and shrubs, rather than pioneer species. https://lh5.googleusercontent.com/PuVEc80hp19uLZPOMPgpMXauj5ZaxXzhu48ZfNSWFENQo rjooiaXyNA2cv7ZOeA7tBTo8-wDwRKKzdqGX_KRpf2-AikFCy946o-Qfi6yIlYvr_Wx913WJ6Psi1dl PUErSwVktDkX

Secondary Succession. https://commons.wikimedia.org/wiki/File:Secondary_Succession.png

A keystone species is one which has a substantial effect on maintaining ecological balance in an environment despite a relatively low abundance. A keystone predator maintains this balance by hunting other species to prevent their overabundance (and subsequent damaging effects on other species present).

Biomes A biome is a large area of land or water defined by its biotic factors (plant and animal populations), which are adapted to the climate and geography (rainfall, temperature, soil, sunlight, etc.) ****of that region. Biomes exist on land (terrestrial biomes) and in water (aquatic biomes).

All of the abiotic factors described above (soil, sunlight, temperature, and rainfall) affect ecosystem distribution. However, rainfall and temperature have the most important effect on biome distribution. This is because areas with similar latitudes can have radically different biomes, even though they receive about the same amount of sunlight. This brings us to the concept of a climograph, which allows us to examine annual changes in rainfall and temperature on a single graph. https://lh6.googleusercontent.com/OgKiTmBfOeDtpiArriLV_Gr8LNf5z1CY_OQ67LFRdOjaYQ_d oOqdcg397633dq7dhjg1UI_l7FdBnMg10rr_tUrkKa_0FBg1KY47rqmP53XT1iLgYGFO_JZcMl6P D6m7gumaeqGx https://commons.wikimedia.org/w/index.php?curid=8967406 Usually, a climograph will combine a bar graph and a line graph, where the bar graph represents average monthly precipitation and the line graph represents average monthly temperature. The x-axis of a climograph typically shows the month, and it is used for both the bar and line graphs. However, the y-axes are a little different - the y-axis to the left of the graph is to be used to represent one data set (often precipitation data - the bar graph), while the y-axis to the right is to be used for the temperature data (line graph). In this way, a climograph is a useful tool to compare the two most important factors with respect to biome distribution (temperature and rainfall). The climograph in our example image from

above represents a savanna (which we will define below) because there are relatively high temperatures all year long, and there is seasonal rainfall. Areas of the Sahara Desert, the lush tropical forests of Central America, and the mountainous, snowy biomes of Nepal are located at similar latitudes and thus receive similar amounts of sunlight; however, these biomes are quite different from each other. The main differences between them are temperature (often due to differences in altitude) and rainfall. Keep climate in mind as you review the terrestrial and aquatic biomes.

Terrestrial Biomes: https://www.youtube.com/embed/A495e31cDdE?rel=0&showinfo=0 This video is licensed by Khan Academy under CC BY-NC-SA 3.0 US at https://creativecommons.org/licenses/by-nc-sa/3.0/us/. The original version can be found at https://www.youtube.com/watch?v=A495e31cDdE.

Try not to get caught up in the details of this table. For the DAT, it is important to have a basic “picture” of what each of these biomes looks like. Remember, it is a multiple choice test; common sense should help you eliminate at least a couple of the answer choices if you have a basic understanding of the biomes.

Aquatic Biomes: Aquatic biomes cover around 75% of the Earth and are therefore the largest of Earth’s biomes. The vast amount of photosynthetic algae that live within these huge aquatic biomes contribute most of the Earth’s atmospheric oxygen. These can be saltwater or freshwater.

In contrast to a saltwater biome, an aquatic biome is considered a freshwater biome if it has a salt content of less than 0.1%. However, these account for just 3-4% of all aquatic biomes. Between saltwater and freshwater biomes you may find an estuary - where freshwater from a coast (via a river or stream) meets a saltwater ocean. Additionally, where the ocean meets land, you find an intertidal zone – this zone is above water at low tide and below water at high tide.

Sunlight greatly influences aquatic ecosystems. Deeper parts of the ocean receive less light, and this has an effect on which plants and animals can survive there. In fact, the layers of the ocean are categorized based on the amount of sunlight they receive. From superficial to deep, these layers are: the euphotic zone, the disphotic zone, and the aphotic zone.

The euphotic zone is closest to the surface. It receives strong irradiance (and heat) from the sun; plants are able to survive and undergo photosynthesis. The littoral zone is the part of the euphotic zone where sunlight penetrates all the way down to the floor of the ocean.

Below the euphotic zone is the disphotic zone. It is semi-irradiated with sunlight, but there is not sufficient sunlight for most plants to survive here. However, some of the light in this zone is from bioluminescent species (you may have heard of Aequorea victoria, the bioluminescent jellyfish from which the famous green fluorescent protein was isolated).

From the bottom of the disphotic zone to the ocean’s floor is the aphotic zone. Almost no light penetrates this layer. Because there is so little sunlight, photosynthetic plants cannot survive here. Like the disphotic zone, there are some bioluminescent species present in this zone. While they are few, select fish species are able to survive here by living off of dead matter that has sunk to the ocean’s floor. https://lh3.googleusercontent.com/fYZQ8__tt18SOkGXMsLSsNWDwKYBRGPy66VABSh0PUJv 4teQ3Z8AYwyM1wgec4z1UdhGDvG3n20Zn6qXqAdryG3PYB1g-Mae6jf8QJ7xqKQLz8uIzquB4 NDC9bJQAc_JOz-ODleO https://commons.wikimedia.org/wiki/File:Primary_zones_of_a_lake.png...