POPULATION DYNAMICS

• Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes.

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ECOLOGICAL SUCCESSION

• Ecological succession is the observed process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction.

Changes in an ecological community over time

TWO MAIN TYPES • Primary Succession

• Secondary Succession

CLIMAX COMMINITIES

• An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment. A climax community is the final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference.

The Daintree Rainforest in Queensland, Australia is an example of a climax forest ecosystem.

BIOMES

• Biomes are defined as "the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment" (Campbell).

• A fundamental classification of biomes are:

• Terrestrial (land) biomes which includes grassland, tropical rainforest, temperate and tundra

• Aquatic biomes (including freshwater biomes and marine biomes)

The Terrestrial

Biomes

Terrestrial biomes are distinguished primarily by their predominant vegetation, and are mainly determined by temperature and rainfall.

• Although few animals and plants are adapted to the extremely dry desert life, the desert is a vital biome. The desert is important because it covers about a fifth of the earth's surface! There are both hot and cold deserts. Antarctica is the largest desert in the world, while the Sahara in Africa is the largest of the hot deserts. .

DESERTS OR DUNES

• Subtropical desert. These occur in the subtropics, from 23.5 to about 30o latitude, generally on the western side of the continents, where high pressure prevails. This high pressure pushes moisture away from these areas. Examples of this type of desert are the Sonoran (SN), Chihuahuan (CU), and Mojave (MH) deserts.

• Rain shadow desert in which a mountain range blocks moisture from reaching the downstream desert. An example of this type is the Great Basin Desert.

Types of Desert

• Taiga - Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present

TAIGA

• Rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

RAINFOREST

• Temperate forest and rainforest - Forests occuring at temperate latitudes (>23.5 degrees N or S latitude). This terrestrial biome is characterized by moderate to large seasonal changes in temperature; rainfall, however, is usually more evenly distributed. Leaves of deciduous trees drop during autumn and winter. Temperate rainforests may experience less seasonal change in temperature.

• Tropical rainforest - A terrestrial biome found within 23.5? of the equator in areas where rainfall is abundant (more than 250 cm/year) and the dry season, if any, is brief. Forests are very diverse floristically and structurally; trees sometimes reach great heights. Most trees are evergreen; deciduous species, if present, do not all lose their leaves at the same time of year.

Types of Rainforest

• An area dominated by grasses, such as a prairie or meadow.

• Temperate grassland - A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

• Tropical savanna and grassland - Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

GRASSLAND

• The tundra biome is the coldest of all biomes.

• The tundra covers about one fifth of the land on earth.

• The word tundra comes from a Finnish word that means treeless plain, which is a good description of the biome.

TUNDRA

•Tundra communities are found within the Arctic Circle and on high mountaintops at all latitudes due to the similar conditions there. • Mosses, lichens, and grasses thrive, but large plants are rare since their roots cannot penetrate the permafrost or absorb water and nutrients from it.

• Arctic tundra (T) is found in the northernmost latitudes where harsh cold and permafrost prevent tree growth. Despite the common appearance of snow much of this biome is actually very dry, often qualifying as desert.

• Alpine tundra (A) is at the highest altitudes on mountains. Alpine tundra gets a great deal of snow, usually from September to July, and has a very short growing season.

Types of Tundra

• Forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

FOREST

• Temperate forest - Forests occuring at temperate latitudes (>23.5 degrees N or S latitude). This terrestrial biome is characterized by moderate to large seasonal changes in temperature; rainfall, however, is usually more evenly distributed. Leaves of deciduous trees drop during autumn and winter.

• Tropical deciduous forest - A terrestrial biome similar to tropical rainforest and found at the same latitudes, but rainy and dry seasons are more distinct and the total amount of rainfall is usually less. Most trees are deciduous and drop their leaves during the dry season. Thorny vegetation is sometimes prominent.

Types of Forest

• Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

CHAPARRAL

Aquatic

biomes

Aquatic biomes

• Water is the common link among the five biomes and it makes up the largest part of the biosphere, covering nearly 75% of the Earth's surface.

• Aquatic regions house numerous species of plants and animals, both large and small.

• Without water, most life forms would be unable to sustain themselves and the Earth would be a barren, desert-like place. Although water temperatures can vary widely, aquatic areas tend to be more humid and the air temperature on the cooler side.

• The aquatic biome can be broken down

into two basic regions:

1. Freshwater

2. Marine

• Freshwater:

▫ Ponds and lakes

▫ Streams and rivers

▫ Wetlands

▫ Marine:

Oceans

Coral reefs

Estuaries

Freshwater Regions

• Freshwater is defined as having a low salt

concentration, usually less than 1%.

• Plants and animals in freshwater regions are

adjusted to the low salt content and would

not be able to survive in areas of high salt

concentration (i.e, ocean).

Ponds and Lakes

• Many ponds are seasonal, lasting just a

couple of months (such as sessile pools)

while lakes may exist for hundreds of

years or more.

• Ponds and lakes may have limited

species diversity since they are often

isolated from one another and from

other water sources like rivers and

oceans.

• Lakes and ponds are divided into three

different “zones” which are usually

determined by depth and distance from

the shoreline.

• The topmost zone near the shore of a

lake or pond is the LITTORAL ZONE.

• This zone is the warmest since it is shallow

and can absorb more of the Sun’s heat.

It sustains a fairly diverse community,

which can include several species of

algae, rooted and floating aquatic

plants, grazing snails, clams, insects,

crustaceans, fishes, and amphibians.

• The near-surface open water

surrounded by the littoral zone is the

LIMNETIC ZONE.

• The limnetic zone is well-lighted (like the

littoral zone) and is dominated by

plankton, both phytoplankton and

zooplankton.

• A variety of freshwater fish also occupy

this zone.

• Plankton have short life spans, when

they die, they fall into the deep-water

part of the lake/pond, the PROFUNDAL

ZONE.

• This zone is much colder and denser

than the other two. Little light penetrates

all the way through the limnetic zone

into the profundal zone.

• The fauna are heterotrophs, meaning

that they eat dead organisms and use

oxygen for cellular respiration.

Streams and Rivers

• These are bodies of flowing water

moving in one direction. Streams and

rivers can be found everywhere, they

get their starts at headwaters, which

may be springs, snowmelt or even lakes,

and then travel all the way to their

mouths, usually another water channel

or the ocean.

• The water is also clearer, has higher

oxygen levels, and freshwater fish such

as trout and heterotrophs can be found

there.

• Towards the middle part of the

stream/river, the width increases, as

does species diversity, numerous

aquatic green plants and algae can be

found.

Wetlands

• Wetlands are areas of standing water

that support aquatic plants. Marshes,

swamps, and bogs are all considered

wetlands. Plant species adapted to the

very moist and humid conditions are

called hydrophytes. These include pond

lilies, cattails, sedges, tamarack, and

black spruce.

• Wetlands have the highest species

diversity of all ecosystems. Many species

of amphibians, reptiles, birds (such as

ducks and waders), and furbearers can

be found in the wetlands.

Marine Regions

• Marine regions cover about three-

fourths of the Earth’s surface and

include oceans, coral reefs, and

estuaries.

• Marine algae supply much of the world’s

oxygen supply and take in a huge

amount of atmospheric carbon dioxide.

Oceans

• The largest of all the ecosystems, oceans

are very large bodies of water that

dominate the Earth’s surface. Some say

that the ocean contains the richest

diversity of species even though it

contains fewer species than there are

on land.

• Like ponds and lakes, the ocean regions

are separated into separate zones:

intertidal, pelagic, abyssal, and benthic.

• The INTERTIDAL ZONE is where the ocean

meets the land—sometimes it is

submerged and at other times exposed,

as waves and tides come in and out.

• The PELAGIC ZONE includes those waters

further from the land, basically the open

ocean. The pelagic zone is generally

cold though it is hard to give a general

temperature range since, just like ponds

and lakes, there is thermal stratification

with a constant mixing of warm and

cold ocean currents.

• The BENTHIC ZONE is the area below the

pelagic zone, but does not include the

very deepest parts of the ocean. The

bottom of the zone consists of sand, slit,

and/or dead organisms.

• The deep ocean is the ABYSSAL ZONE.

The water in this region is very cold

(around 3° C), highly pressured, high in

oxygen content, but low in nutritional

content. The abyssal zone supports

many species of invertebrates and

fishes.

Coral Reefs

• Coral reefs are widely distributed in

warm shallow waters. They can be found

as barriers along continents, fringing

islands, and atolls.

• Naturally, the dominant organisms in

coral reefs are corals. Corals are

interesting since they consist of both

algae and tissues of animal polyp.

• Besides corals, the fauna include several

species of microorganisms,

invertebrates, fishes, sea urchins,

octopuses, and sea stars.

Estuaries

• Estuaries are areas where freshwater

streams or rivers merge with the ocean.

This mixing of waters with such different

salt concentrations creates a very

interesting and unique ecosystem.

• Microflora like algae, and macroflora,

such as seaweeds, marsh grasses, and

mangrove trees (only in the tropics), can

be found here.

• Estuaries support a diverse fauna,

including a variety of worms, oysters,

crabs, and waterfowl.

Biodiversity

• "Biodiversity" is most commonly used to

replace the more clearly defined and

long established terms, species diversity

and species richness. Biologists most

often define biodiversity as the "totality

of genes, species, and ecosystems of a

region

• It is the variability among living organisms

from all sources including, inter alia,

terrestrial, marine and other aquatic ecosystems and the ecological complexes

of which they are a part; this includes

diversity within species, between species,

and of ecosystems.

IMPORTANCE OF

BIODIVERSITY

• Biodiversity boosts ecosystem

productivity where each species, no

matter how small, all have an important

role to play.

• A larger number of plant species means

a greater variety of crops

• Greater species diversity ensures natural

sustainability for all life forms

• Healthy ecosystems can better

withstand and recover from a variety of

disasters.