5 .Coastal decay and dam problems

The effect of water currents and waves on coastal decay:

1. The water returning towards the sea carries sand and pebbles with it.

2. When the water reaches still water, it gradually loses its velocity and deposits the pebbles first then sand while fine particles sediment away from the shore in deep layers.

3. Soft rocks are subjected to greater erosion than harder ones.

4. This repetitive process decays the coast while the ocean creeps gradually inwards , a wide plain slopes slowly towards the sea.

5. The tide decays the high regions of the coast where waves cannot reach.

6. Coastal decay at Rosetta and Damietta increased after the construction of the High Dam.

Dams, reservoirs, storage lakes are constructed for:

• development of agriculture

• Production of energy

• Storage of water for time of need.

Advantages of the High Dam :

• Protected Egypt against flooding & drought .

• Saved water needed for agriculture.

• Produced Electric power (it provides Egypt with about 70% of electrical energy).

Disadvantages (Negative effects) of the high Dam :

• Spread of water weeds in canals.

• Increase in soil salinity.

• Absence of clay.

• Increase of atmospheric humidity over Nasser’s lake.

• Emigration of Nubian citizens from South to North

Chapter 4

Variation of living organisms & their classification

Taxonomy:isthe science of classifying organisms & arranging them in groups

according to their similarities.

John Ray classified living organisms according to similarities in their external features. The unit of classification is the species.

T he species is a group of individuals with similar morphological characteristics & parents characteristics.

The new system of classification puts the organism in the following series

Kingdom

Phylum

Class

Order

Family

Genus

Species.

S wedish physician and naturalist Carolus Linnaeus developed a method for classifying plants using a binomial method of scientific names. His classification simplified the way in which organisms were named by organizing them into meaningful groups based upon their physical similarities. Many of his classifications are unchanged to the present day. Linnaeus believed that species did not change over time, but modern scientists use his classification system to indicate evolutionary relationships. Humans are classified as genus and species Homo sapiens

Greek philosopher Aristotle (384-322 bc) grouped life forms as either plant or animal. Microscopic organisms were unknown.

In 1735 Swedish naturalist Carolus Linnaeus used two Latin names to identify each organism, a system called binomial nomenclature. He grouped closely related organisms and introduced the modern classification groups: kingdom, phylum, class, order, family, genus, and species. Single-celled organisms were observed but not classified.

• In 1866 German biologist Ernst Haeckel proposed a third kingdom, Protista, to include all single-celled organisms. Bacteria, which lack nuclei, were placed in a separate group within Protista called Monera.

• In 1938 American biologist Herbert Copeland proposed a fourth kingdom, Monera, to include only bacteria. This classification separates organisms

Prokaryotes Eukaryotes

Without nuclei With nuclei

• In 1957 American biologist Robert H. Whittaker proposed a fifth kingdom, Fungi, based on fungi's unique structure and method of feeding. Fungi do not ingest food as animals do, nor do they make their own food, as plants do; they secrete digestive enzymes around their food and then absorb it into their cells.

The old system of classification	The new system of classification
1. Linnaeus proposed this system.	1. Whittaker proposed this system.
2. Classified organisms into 2 kingdoms animals & plants therefore couldn't classify bacteria & algae.	2.Classified organisms into 5 kingdoms : monera , protista , fungi, animals & plants .
3. The species doesn't change over time.	3. The species can evolve into a new species over time.

The objections against the old classification

1. S ome organisms couldn't be classified as plants or animals such as bacteria.

2. The old system assumes that each species is stable & doesn't change over time . Recently some scientists believe that new species evolve from old ones.