Populations and communities Topic 4: Distribution and Abundance

1. Populations and communitiesTopic 4: Distribution and Abundance Part of the Local Ecosystems Module Spotlight Biology Preliminary Text Chapter 3 Authors: D. Heffernan, J. Bastina, B. Grieve, K. Humphreys, A. Sartor Science Press 2002

2. Distribution and Abundance Distribution of a species is where a species lives, how it’s ‘distributed’ on a continent. Abundance is the number of species living in an area. -For example, a red river gum tree is distributed all over Australia. However it is more abundant along river courses. jawdesign.net

3. Distribution and Abundance There are many factors that affect the distribution and abundance in terrestrial and aquatic environments including: • Availability of food • Abundance and range of predators • Competition for food and resources • Climate conditions (temp/rainfall) • Chemical conditions (pH/availability of gases) • Parasites and disease

4. Distribution and Abundance Both distribution and abundance can change from year to year. When the Menindee Lake System floods, there are flocks of pelicans nesting in the remote desert environment of Western NSW. When the system dries out, they move to other areas where there is water. abc.net.au

5. Distribution and Abundance The abundance can also change even if the distribution doesn’t. When mouse populations reach plague proportion the abundance of mouse eating organisms like snakes increase. When food for the mice runs out, their numbers decline and so does that of the snakes. smh.com.au

6. The Forests ‘Terrestrial Ecosystems’ Land areas that include mountains, valleys, plains, deserts, grasslands and forests are referred to as ‘terrestrial ecosystems’. Places on land where organisms live. theodora.com

7. The Forests Forests are areas high in rainfall and have many plants and animals with interesting adaptions. The leaf litter alone supports a range of organisms that are important to the balance of the entire ecosystem. There are many factors that influence distribution and abundance in these terrestrial environments. (We’ll discuss these in more detail next module) forestsandclimate.net

8. Plants of the Forest The forests in Australia can be divided into 4 main types: • Open forests • Tall, Closed forests • Temperate rainforests • Tropical rainforests **Hand out ‘Vegetation types across NSW Table’ (pg 78 Spotlight Text) journeyjottings.com

9. Plants of the Forest Open Forests • Contain relatively short, somewhat knotted eucalypts and an understory of drought-resistant shrubs. They grow in drier regions with poor soil. Around Sydney they are found on porous sandstone ridges. permaculture.org.au

10. Plants of the Forest Tall, closed forests • Contain taller and straighter eucalypts. Because of the fairly closed canopy above, less light reaches the softer leaved shrubs beneath. Wet sclerophyll forests generally grow on better soils with moderate rainfall. drytropics.org

11. Plants of the Forest Temperate Rainforests • Exist in cooler, higher rainfall areas where the soil is good. The eucalypts are often very tall and straight, and a number of other larger tree types may be present. There may also be a well-developed understory of ferns. environment.nationalgeographic.com

12. Plants of the Forest Tropical Rainforests • Exist in the warmer areas of extreme rainfall. They contain few if any eucalypts. There is no understory because the light intensity beneath the dense tree canopy is very poor. The diversity of trees can be huge. 1 hectare can contain more than 200 different species. biomee.wikispaces.com

13. Animals of the Forest Many animals that live in forests have adaptations for living in trees. Here are a few examples: • Lizards: Special pads on their toes and feet, and some have large claws • Frogs: Have suction cups on their toes • Possums have sharp claws and large folds between their les that allow them to glide from tree to tree. • Kaolas have large claws and large back legs.

14. Animals of the Forest Animals of the forest floor are also very interesting. This includes: • Wombats • Bandicoots • Wallabies A few that survive on termites and ants include: • Anteater • Numbat • Echidna australianstamp.com

15. Freshwater Streams Freshwater streams are also a part of our forests. Aquatic ecosystems include the oceans, estuaries, coral reefs, lakes and freshwater streams. Many factors affect the distribution and abundance of organisms in these ecosystems. nomoresweden.com

16. Freshwater Streams Several important factors that affect the distribution and abundance of organisms in freshwater streams include: • Rate of flow • Nature of the rock along the bottom • Amount of sediment • Levels of dissolved minerals • Levels of dissolved oxygen jasonwotherspoon.com

17. Plants of Freshwater Streams Many of the plants in our fresh water streams are microscopic phytoplankton (algae). Algae are the start of nearly all food chains. Algae attached to rocks and logs are more important in flowing streams and free floating algae is more important in lakes and swamps. redsquarepools.wordpress.com

18. Plants of Freshwater Streams Another source of plant matter in freshwater streams are the plants growing along the banks. They contribute potential food when their leaves and branches fall into the water. Rushes and sedges including cumbungi and fallen trees provide habitat for fish and other organisms. brg.cma.nsw.gov.au

19. Animals of Freshwater Streams Freshwater streams are home to many species of fish which include: • Perch • Cod • bony bream. These streams are also home to many invertebrates which include: • Waterboatman • Whirligig beetle • Backswimmer • Waterstrider curiouschemeng.blogspot.com

20. Animals of Freshwater Streams Waterstriders have fine hairs on the ends of their legs to prevent them from breaking the surface tension of water. This allows them to ‘stride’ across the top. Backswimmers lie on their backs and use their legs like paddles to get around in the water. They have eyes adapted to viewing above and below the water. nathistoc.bio.uci.edu

21. Homework Answer the following questions your notebooks. Come to class prepared to discuss next lesson. Remember you will also be marked as attempting/not attempting these. • Contrast distribution with abundance • Identify the factors which determine the distribution and abundance of a species in either a terrestrial of aquatic environment. • Construct a table to compare the following abiotic factors of aquatic and terrestrial environments: Availability of oxygen, temperature variation, pressure variation, viscosity, light penetration, buoyancy and availability of ions (hint: See the handout I gave you. Reconstruct in your own words though!)