Chromosome

Eukaryotic DNA

• DNA in the eukaryotic cell is packaged in the form of chromatin. Which forms a chromosome.
• Chromatin is a complex of DNA and histone proteins
• DNA is wrapped around a core of 8 histone protein molecules, and linked to a H1 histone protein.
• Each of this units is called a nucleosome

This continuing chain of nucleosomes is attached to a protein scaffold.
This scaffold loops around itself, eventually forming a chromosome.

Ecology

Ecology Index:

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Table of Contents:

• Intro To Ecology
• Nutrient Cycles:
• Ecosystem Types:
• Ecological Succession
• Population Ecology
• Global Warming
• Ozone Depletion
• Acid Rain

Acid Rain

Acid Rain

• Closely tied to the water cycle
• Emmissions mostly from burning of fossil fuels release SO₂ (Sulphur Dioxide) and NO_N (Nitrogen Oxides) into the atmosphere.

Sources of pollutants

• These compounds react with the H₂O in the clouds forming H₂SO₄ (sulfuric acid), and HNO₃ (Nitric acid).

• These acids then precipitate in the form of rain and collect in fresh water lakes.

• Over time this lowers the pH of the lakes, killing off most of the aquatic wildlife.

pH of acid rain

• This rain can also alter the pH of sensitive soils killing trees, and damaging forests

Acid rain damaged forest

Ozone Depletion

Ozone Depletion

• Caused mainly by emmissions of CFC's into the atmosphere.
• Main Sources of CFC's are
• Aresol can propellants
• Refrigerant gasses

• CFC's enter the atmosphere and destroy Ozone (O₃)

• Ozone blocks harmful Ultraviolet Light (UV) from entering the atmosphere.
• Over time this has caused ignificant "Ozone holes" over the polar regions of the earth, and these are becoming larger.

Scientists fear that increased UV levels could cause increases in cancer rates in affected areas.

Global Warming

Global Warming

• Caused By Excess CO₂ in atmosphere generally caused by burning of fossil fuels by automobiles or industry.

• CO₂ traps heat energy in the atmosphere slowly increasing global temperature via the Greenhouse Effect

• Visible light passes through atmosphere to surface heating it.
• Infared (heat) energy cannot pass out so easily and is trapped. Increasing the global temperature.

 

• Global temperatures may have risen approx. 3⁰C overt the lact century

• Overall concern is that warming may cause melting of the polar ice caps. This would raise the sea level and cause gradual flooding of areas close to sea level. Already very large portions of ice have split from the ice sheets in Antactica and Greenland.

Iceberg the size if Rhode Island calving from the Greenland Ice Sheet

Population Ecology

Population Ecology

Vocabulary/Definitions:

• Population: All individuals of a single species which exits in the same geographical area at the same time.

Population size and dispersion:

• Population size greatly effects survivability of a species.
• Greater the population size - Better probability of the species
• Reduces effects of inbreeding
• Reduces effects of catastrophic random events.
• Population density is another important factor
• Effects probability of individuals meeting, mating and combining genetic materials.
• Population dispersion is a measure of the geographical arrangement of the individuals within a population
• 3 types
• Randomly spaced - No apparent pattern to individual locations
• Evenly spaced - Individuals are located individually according to an observable pattern
• Clumped - Small populations occur in close proximity to each other. Each group, however, is separated from similar groups

Population Growth:

• Population growth occurs as an exponential function. It is characterized by a slow initial population growth called the lag phase, followed by an explosive increase of population called the log phase.

• In a healthy ecosystem limiting factors cause the curve to reach a stable plateau. This maximum population an ecosystem can support is called the carrying capacity

In a less than healthy ecosystem the population undergoes a crash phase where toxins, disease or starvation cause a dramatic population drop.

Ecological Succession

Ecological Succession

Refers to the general metamorphosis of a geographic area to its most stable ecosystem.

• Primary succession refers to the settlement/establishment of vegetation in an area previously uncolonized by organisms. Organism which first colonize an area are known as pioneer organisms.

• Primary succession which occurs on land is termed Xerarch succession. That which occurs from aquatic ecosystems is known as hydrarch succession

• Secondary succession refers to the recolonization of a geographic area, which had been previously sett;led, but somehow disrupted.
• Some causes of disruption include
• Fire
• Volcanism
• Severe weather
• Agriculture
• Development

• Both processes result in the most stable type of biome given its geographical location. This is called a climax community.

Types of Ecosystems

Types of Ecosystems

• There are many types of ecosystems on earth.
• Major classes of relatively contained ecosystems are called Biomes.
• There are 3 Major classes of ecosystems

1. Freshwater Ecosystems
2. Terrestrial Ecosystems
3. Ocean Ecosystems

Freshwater ecosystems:

• Relatively small in area ~ 1.8% of earth's surface
• Support many species of life including fish, amphibians, insects and plants.
• Base of food-web is found in freshwater Plankton (small microscopic organisms)

Terrestrial Ecosystems:

• Many & diverse types of ecosystems. There are seven major types.
• Location usually dependent on the latitude of the area, and amount of precipitation

types & locations of biomes

Types:

1. Tropical Rain Forest

• Precipitation - 250cm/year
• Little temp. variation/abundant moisture
• Contains more species than other biomes.

tropical rain forest

1. Savannas

Precipitation 90-150cm/year
Open, widely spaced trees, seasonal rainfall
Parts of Africa, South America & Australia
3. Deserts Precipitation 20cm/year
Dry, sparce vegetation; scattered grasses
Parts of Africa, Asia, Australia, North America

Desert

1. Temperate Grasslands
Precipitation: 10-60cm/year Rich soil; tall dense grasses Central North America; Central Asia
2. Deciduous forests
75-250cm/year Warm summers, cool winters Europe; NE United States;Eastern Canada

Temperate/Deciduous forest
3. Coniferous forest:
20-60cm/year Short growing season, cold winters. Northern Asia;Northern North America

Coniferous Forest
4. Tundra

25cm/year
Open; wind swept; dry; ground always frozen
Far northern Asia; Northern North America

Tundra

Ocean Ecosystems:

• Very large amount of Earth is covered by ocean (~75%)
• 40% of all photosynthesis occurs in oceans.
• 3 types of oceanic ecosystems
• Shallow ocean waters
• Deep ocean water
• Deep ocean surface.
• Photosynthetic plankton is base of food chain.
• Only occurs in Deep ocean surface & Shallow ocean ecosystems
• No photosynthesis can occur in deep ocean because light cannot penetrate deeply into water.

Nutrient Cycles

Nutrient Cycles:

• In all ecosystems, Nutrients are used by organisms and eventually returned to it again.
• These are known as the nutrient cycles.
• There are 3 well known of these cycles.

1. The Water Cycle.
2. The Nitrogen Cycle.
3. The Carbon Cycle.
4. The Phosphorous Cycle

The Water Cycle

• Water is the most important non-organic component of an ecosystem.
• Plants play an important role in retaining water in an ecosystem.

• In this cycle the following occurs.
• Rain falls to earth either runs off to the ocean, evaporates into air, or is held by plants and is transpired back into the atmosphere. (90% of the water which passes into an ecosystem passes through plants).
• Evaporated moisture (from land, plants & ocean) condenses in the form of clouds and returns to land in the form of precipitation.

The Nitrogen Cycle

• Nitrogen is an important component in the production of proteins.
• Most nitrogen is inert and unusable by plants & animals.
• Certain bacteria known as Nitrogen fixing bacteria, have the ability to convert N₂ gas, into NH₃ (ammonia) which is a usable form of Nitrogen.
• These bacteria are often decomposers, and release ammonia when an animal is decomposing.
• Others live in the roots of certain plants in a symbiotic relationship.(eg peanuts). The bacteria provides Nitrogen compounds for the plant. The plant proivides food for the bacteria.

The Carbon Cycle:

• Carbon is the building block of all organic molecules.
• Carbon cycle is based on the creation and absorption of CO₂ (carbon dioxide).
• CO₂ is produced by plant & animal respiration & by combustion (fires, industry, cars, etc…)
• CO₂ is absorbed by plants and converted to food (sugars) by plants through photosynthesis.
• This food is, in turn, converted back to CO2 through respiration by plants & animals.

The Phosphorous Cycle:

• Phosphorous is a critical mineral in plant growth. Due to its scarcity it often is a significant limiting factor in plant growth.
• Often Phosphate-Rich detergents can disrupt an aquatic ecosystem by stimulating algeal blooms, choking off light to lower levels of water.

Ecology

Ecology

Vocabulary:

• Ecology - The study of how organisms fit into their environment.
• Community - The organisms which live in a particular environment.
• Habitat - Physical location of a community
• Ecosystem - Self-sustaining collection of organisms & their physical environment.
• Diversity - a measurement of the number of organisms inhabiting an ecosystem

Energy in ecosystems:

• Life in any ecosystem is driven by the flow of energy.
• All energy entering the earth's Biome is from the sun.
• Living things are divided into 3 major categories based on how they obtain their energy

1. Producers - Obtain energy from their surroundings (eg.light)
2. Consumers - Obtain energy from consuming other organisms
3. Decomposers - Obtain energy from consuming wastes.

• Energy in an ecosystem always flows from producers to consumers
• Organisms are assigned "trophic levels" according to how many "steps" they are away from the source of their energy.
• Autotrophs (like plants) occupy the first level since they obtain their energy directly from the source
• Herbivores occupy the second level, since they obtain their energy from eating the autotrophs.
• Carnivores occupy all higher levels, since they obtain energy from eating herbivores (and other carnivores)
• Omnivores can occupy more than one trophic level since they can eat all of the above.

Note: All organisms above the the first trophic level are known as heterotrophs since they cannot make their own food, but must obtain it by consuming other organisms.

• Energy flow across trophic levels is inefficient - Energy is lost between each level.
• Only about 1/10 makes it from 1 level to the next.

Food Webs
Energy moves through an ecosystem in a complex pattern. The interactions of energy flow is best viewed as a food web.

Kingdom Plantae

Kingdom Plantae

Index

• Introduction
• Division Bryophyta
• Seedless Vascular Plants
• Gymnosperms
• Angiosperms
• Cell & Tissue types
• Stems
• Leaves

Leaf Structure

Leaf Structure

• Leaf is a complex structure designed to maximize photosynthesis & minimize H₂O loss.

• Composed of 2 major systems.
• Dermal System
• Fundamental System

Dermal System

• Functions to allow gas exchange & protect plant
• Composed of Cuticle & Epidermis
• Cuticle is a waxy waterproof layer
• Reduces water loss
• Prevents parasites from entering plant
• Epidermis is the outermost layer of cells of the leaf
• Contain unusual structures called stomata
• Stomata are openings allowing gas exchange in/out of leaf
• Are opened and closed by function of 2 guard cells
• In high heat or arid conditions guard cells close stomates reducing water loss

Stomates

Fundamental System

• Also known as the Mesophyll
• Contains 2 major tissue layers
• Palisade parenchyma
• Major fxn: Photosynthesis
• Spongy parenchyma
• Fxn: some photosynthesis, also storage and transport
• Mesophyll also contains vascular bundles consisting of
• Bundle sheath
• Xylem & phloem

Cross Section of a Leaf

Stems

Stems

• Plant stems vary according to dicot and monocot.
• Stems show both primary & secondary growth.
• Primary growth is extension along a stem


• Tissues where this growth occurs are called primary meristems
• Secondary growth occurs as an increase in diameter of the stem
• Tissues where this occurs are called secondary meristems

Structure of the stem

External Structure of a Stem

Monocot Stems

• Monocot Stems are characterized by Vascular Bundles evenly distributed throughout the ground tissue
• Vascular bundles are composed of both xylem & phloem and surrounded by a bundle sheath.

Monocot Stem

Dicot Stems

• Dicot stems are characterized by vascular bundles distributed radially around the stem perimeter
• Vascular bundles consist of a layered design
• Phloem tissue is located closest to the epidermis
• Vascular cambium (site of secondary growth) is located nearer the center
• Xylem tissue located nearest the center

• Woody Stems show similar tissue patterns.
• Develop a layer of bark outside the epidermis of the stem
• Develop annual rings which show growth of the tree over long periods of time.

Plants: Cell & Tissue Types

Plants: Cell & Tissue Types

• Plants are generally composed of specialized tissue types
• Some tissues are composed of 1 type of cell - simple tissues
• Some composed of more than one - complex tissues

Cell types
Parenchyma

• Most common cell found in most plants
• Have many functions
• Storage
• Photosynthesis
• Secretion
• Have thinner, evenly thickened cell walls

Parenchyma cells

Collenchyma

• Less common than Parenchyma
• Function is primarily support (but this is flexible tissue)
• Have unevenly thickened cell walls (esp. at corners)

Collenchyma cells

Sclerenchyma

• Less common than both above cell types
• Are used exclusively for rigid support
• Have primary cell walls, and thick secondary cell walls

Sclerenchyma cells

Complex Tissue Types
Xylem
Are conducting tissues in plants
Conduct H₂O and minerals upwards into plant
Are complex tissues consisting of parenchyma, and 2 specialized cells vessel elements & tracheids
Are long hollow cells which are dead at maturity

Vessel Elements & Tracheids

Phloem

• Another conducting tissue in plants
• Conducts food throughout plant
• Complex tissue consisting of 4 types of cells
• Seive tube members
• Are long cells connected end-to-end dead at maturity
• Connected by seive like ends called seive plates
• Companion cells
• Located next to Seive tubes
• Assist in moving nutrients and H2O in-out of seive tubes
• Fibers
• Function for support
• Parenchyma

Seive tube members & Companion cells

Summary of Cell & Tissue types

Angiosperms

Division Magnoliophyta: The Angiosperms

• Vascular plants possessing flowers, fruits & seeds
• Most successful plants today
• Reproduce sexually by producing seeds within fruits
• Have extremely well developed vascular systems
• Extremely important to humans
• All major human food crops are angiosperms

There are 2 major classes of angiosperms

• Class Liliopsida: The Monocots
• Class Magnoliopsida: The Dicots
• Differ in leaf structure, seed structure, vascularization, & flower structure

The Monocots:

• Monocots are Herbaceous (non woody) plants
• Stems have characteristic vascular system
• Leaves have parallel veination (veins run parallel to each other)
• Flower parts of a monocot occur in multiples of three.
• Seeds have a single cotyledon (embryonic seed leaf) and have endosperm (nutritive tissue)

The Dicots:

• May be herbaceous or Woody.
• Leaves are usually broader and have Netted Veination.
• Flower parts occur in 4 or 5's (or multiples of)
• Seeds have two cotyledons, and usually no endosperm.

Seed types

Stem Types

The Flower:
Flowers have 4 main organs

• Sepals
• Petals
• Stamens
• Carpels (or pistils)

• Flowers which have all 4 parts are called Complete
• Flowers lacking 1 or more parts are called Incomplete

• The main reproductive structures are the stamens and carpels (or pistils)

• Stamens are the male part of the flower
• Composed of 2 parts
• Anther
• Filament
• Contain microspore mother cells which produce microspores which develop into pollen grains

• Pistil or Carpel is the female part of the flower
• Composed of 3 main parts
• Stigma
• Style
• Ovary
• Ovary contains one or more ovules. Each ovule contains a female gametophyte

Life cycle of the flowering plant

• Each ovule contains a megasporocyte which undergoes meiosis to produce 4 haploid megaspores.
• Three disintegrate, the 4^th divides by mitosis to produce a female gametophyte.
• The gametophyte is composed of 8 haploid nuclei. Including:
• 1 egg
• 2 polar nuclei

• The pollen grain is formed from the microspores produced in anther.
• Consists of:
• Tube nucleus
• 2 sperm nuclei

Fertilization:

• Pollen grain pollenates flower
• Tube nucleus develops a pollen tube into the ovule.
• Here unique process of Double Fertilization occurs.
• One sperm nucleus fertilizes the egg forming a zygote.
• This develops into the plant embryo.
• Other sperm nucleus fuses with the 2 haploid polar nuclei to form a TRIPLOID (3N) nucleus.
• This develops into the endosperm of the developing seed.

Double fertilization

Gymnosperms

Gymnosperms

• Are Vascular plants
• 4 divisions of gymnosperms the 3 largest are as follows

1. Conifers - Cone bearing needled trees (eg.pines, firs)
2. Cycads - cone bearing palmlike plants
3. Ginkgos

• Exhibit alternation of generations

• Sporophyte (2N) generation is dominant.
• Produce true seeds
• Seed = embryonic sporophyte, stored food & protective coat
• Seeds of gymnospermsare "naked"
• Sporophyte generation produces heterospores - spores are not identical
• Microspore (male) will develop into a pollen grain which later develops into a sperm producing male gametophyte
• Megaspore (female) will develop into an egg bearing female gametophyte.

Life Cycle of the Pine

• Pines produce 2 cones - male & female

• Male cone is smaller and often located in the upper portion of the tree
• Male cone scales contain pollen sacs where microspore parent cells undergo meiosis to make microspores.
• Microspores develop into pollen grains.
• .Female cone is larger (located lower on tree)
• Contain 2 ovules where megaspore parent cells undergo meiosis to form megaspores.
• Only one of 4 megaspores develops into mature gametophyte.

 

• Pollenation.
• Pollen grains are carried by wind to open scales of female cone.
• Pollen grain grows a pollen tube to the mature egg. Where it is fertilized by 2 non motile sperm (only 1 fertilizes egg, other dies). Embryo will develop into a seed.
• Fertilization requires ~15 months.
• After 3 years seed is released and will germinate to form an adult sporophyte.

Pine Life Cycle

Seedless Vascular Plants

Seedless Vascular Plants

• Earliest Vascular plants
• Have true roots and stems
• Have true leaves
• Exhibit alternation of generations, However sporophyte (2N) generation is now dominant over gametophyte (N) generation.
• 4 major divisions
• Division Pterophyta - Ferns
• Division Psilophyta - Whisk ferns
• Division Lycophyta - Club Mosses
• Division Sphenophyta - Horsetails

Division Pterophyta: The ferns.

General Form

• Found throughout the world-more frequently in tropical areas.
• Adult sporophyte has a long horizontal stem called the Rhizome.
• Rhizome is vascular
• Fronds extend upwards from rhizome
• Roots extend downwards from rhizome

Life Cycle

• Spores are released from small structures underneath sporophyte fronds called sori (sorus)
• Spores grow into the gametophyte generation called the Prothallus
• Is heart shaped, ~2cm across.
• Contain archegonia (egg) and antheridia (sperm) similar to mosses.
• Sperm fertilizes egg via rain, sporophyte grows from within archegonia

Fern Life Cycle

Division Psilophyta: The Whisk ferns.

• Similar to ferns in life cycle
• Sporophyte generation develops a "forked" branching pattern called dichotymous branching.
• Leaflike structures lack vascularization

Division Lycophyta: The Club Mosses

Club Moss

• Are usually smaller.
• Life cycle differs from ferns in that gametophytes are either male or female, not both.
• Archegonia are produced on female gametophyte.
• Antheridia are produced on female gametophyte.

Division Sphenophyta: The Horsetails

• Characterized by jointed stems
• Have "Cone-like" structures at tips of stems

Division Bryophyta

Non-Vascular Plants - Division Bryophyta

• Include mosses, liverworts & hornworts
• Are composed of green leaf-like structures
• Have root like structures called rhizoids
• Are non vascular plants


• Do not contain tissues to conduct H₂O (limits their size)

Moss

• Exhibit clear alternation of generations
• Plants reproduce sexually, and are male and female
• Male & female can occur as separate plants or on same plant
• Have a dominant Gametophyte generation
• This generation is haploid (N)
• Produces sperm and egg
• Sporophyte generation is diploid (2N)
• Produces spores ONLY through meiosis (unlike fungi)

Life Cycle of moss (Class Bryopsida)

• Sperm are produced in Male structure called Antheridia
• Eggs are produced in female structure called Archegonium


• Sperm is transferred to archegonium via rain. Feritiization results in a diploid zygote This develops into the sporophyte generation This grows from the interior of the archegonium and is composed of three parts
• Foot (attaches to archegonium)
• Seta - a stalk-like structure
• Capsule - produces spores
• Sporophyte produces spores via meiosis Spores are released and grow into more of the gametophyte generation.

Life cycle of a moss

Class Hepaticophyta: The Liverworts.

• Named due to the fact that the main body or thallus of the plant can be liver-shaped
• Life cycle similar to Brypohytes.
• Produce special structures called Gemmae Cups. Which allow asexual reproduction
• Produce balls of tissue called Gemmae.
• When rain splashes into cups, gemmae are released and can develop into an independent plant

A Liverwort

Liverwort Reproductive Structures

Class Anthroceropsida - The Hornworts

• Very similar to liverworts. But smaller.
• Usually have leafy thallus
• Cells are similar in some respects to algae.
• Usually only have 1 large chloroplast in cells
• Archegonia & Antheridia are usually embedded in the gametophyte thallus

Typical hornwort