diff --git a/game.sqlite b/game.sqlite
index a2f89f7..54b5b4b 100644
Binary files a/game.sqlite and b/game.sqlite differ
diff --git a/server.py b/server.py
index 839e6a2..8780cad 100644
--- a/server.py
+++ b/server.py
@@ -17,3 +17,79 @@
 #    You should have received a copy of the GNU General Public License
 #    along with game.  If not see <http://www.gnu.org/licenses/>.
 #
+import data
+
+
+def turn():
+    conn = data.open_db()
+    cursor = conn.cursor()
+    life_grows(cursor)
+    population_grows(cursor)
+    industry_produces()
+    vessels_move()
+    conn.commit()
+    data.close_db()
+
+
+BIO_GROWTH = 0.03
+POP_GROWTH = 0.0125
+
+def life_grows(db_cursor):
+    print('life_grows')
+    db_cursor.execute('''
+        select id, bio, bio_capacity from planets
+        where bio > 0 and bio < bio_capacity
+        ''')
+    planets = list(db_cursor.fetchall())
+    # Get all the results before updating some in this loop.
+    for planet_id, bio, bio_capacity in planets:
+
+        # We add at least one unit of population per turn.
+        new_bio = round(bio * BIO_GROWTH) or 1
+
+        available_capacity = bio_capacity - bio
+
+        if new_bio > available_capacity:
+            excess_bio = new_bio - available_capacity
+            new_bio = available_capacity
+
+        else:
+            excess_bio = 0
+
+        bio = bio + new_bio
+        assert bio <= bio_capacity
+        print(f'setting planet {planet_id} bio to {bio} increment of {new_bio}, excess_bio {excess_bio}')
+        db_cursor.execute('update planets set bio = ? where id = ?', (bio, planet_id))
+
+
+def population_grows(db_cursor):
+    print('population_grows')
+    db_cursor.execute('''
+        select populations.id, populations.pop, planets.id, planets.bio
+        from populations join planets
+        on populations.planet = planets.id
+        ''')
+    pops = list(db_cursor.fetchall())
+    for pop_id, pop, planet_id, bio in pops:
+        if pop > bio:
+            # famine and death!  Woe!
+            pop = bio >> 1
+            bio //= 10
+        else:
+            bio -= pop  # Everyone eats.
+            new_pop = round(pop * POP_GROWTH)
+            pop += new_pop
+        print(f'population {pop_id} of planet {planet_id} is now {pop}, bio is {bio}')
+        db_cursor.execute('update planets set bio = ? where id = ?', (bio, planet_id))
+        db_cursor.execute('update populations set pop = ? where id = ?', (pop, pop_id))
+
+
+def industry_produces():
+    print('industry_produces')
+
+def vessels_move():
+    print('vessels_move')
+
+
+if __name__ == '__main__':
+    turn()